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diff --git a/arch/tile/include/gxio/mpipe.h b/arch/tile/include/gxio/mpipe.h
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+++ b/arch/tile/include/gxio/mpipe.h
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+/*
+ * Copyright 2012 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#ifndef _GXIO_MPIPE_H_
+#define _GXIO_MPIPE_H_
+
+/*
+ *
+ * An API for allocating, configuring, and manipulating mPIPE hardware
+ * resources.
+ */
+
+#include <gxio/common.h>
+#include <gxio/dma_queue.h>
+
+#include <linux/time.h>
+
+#include <arch/mpipe_def.h>
+#include <arch/mpipe_shm.h>
+
+#include <hv/drv_mpipe_intf.h>
+#include <hv/iorpc.h>
+
+/*
+ *
+ * The TILE-Gx mPIPE&tm; shim provides Ethernet connectivity, packet
+ * classification, and packet load balancing services.  The
+ * gxio_mpipe_ API, declared in <gxio/mpipe.h>, allows applications to
+ * allocate mPIPE IO channels, configure packet distribution
+ * parameters, and send and receive Ethernet packets.  The API is
+ * designed to be a minimal wrapper around the mPIPE hardware, making
+ * system calls only where necessary to preserve inter-process
+ * protection guarantees.
+ *
+ * The APIs described below allow the programmer to allocate and
+ * configure mPIPE resources.  As described below, the mPIPE is a
+ * single shared hardware device that provides partitionable resources
+ * that are shared between all applications in the system.  The
+ * gxio_mpipe_ API allows userspace code to make resource request
+ * calls to the hypervisor, which in turns keeps track of the
+ * resources in use by all applications, maintains protection
+ * guarantees, and resets resources upon application shutdown.
+ *
+ * We strongly recommend reading the mPIPE section of the IO Device
+ * Guide (UG404) before working with this API.  Most functions in the
+ * gxio_mpipe_ API are directly analogous to hardware interfaces and
+ * the documentation assumes that the reader understands those
+ * hardware interfaces.
+ *
+ * @section mpipe__ingress mPIPE Ingress Hardware Resources
+ *
+ * The mPIPE ingress hardware provides extensive hardware offload for
+ * tasks like packet header parsing, load balancing, and memory
+ * management.  This section provides a brief introduction to the
+ * hardware components and the gxio_mpipe_ calls used to manage them;
+ * see the IO Device Guide for a much more detailed description of the
+ * mPIPE's capabilities.
+ *
+ * When a packet arrives at one of the mPIPE's Ethernet MACs, it is
+ * assigned a channel number indicating which MAC received it.  It
+ * then proceeds through the following hardware pipeline:
+ *
+ * @subsection mpipe__classification Classification
+ *
+ * A set of classification processors run header parsing code on each
+ * incoming packet, extracting information including the destination
+ * MAC address, VLAN, Ethernet type, and five-tuple hash.  Some of
+ * this information is then used to choose which buffer stack will be
+ * used to hold the packet, and which bucket will be used by the load
+ * balancer to determine which application will receive the packet.
+ *
+ * The rules by which the buffer stack and bucket are chosen can be
+ * configured via the @ref gxio_mpipe_classifier API.  A given app can
+ * specify multiple rules, each one specifying a bucket range, and a
+ * set of buffer stacks, to be used for packets matching the rule.
+ * Each rule can optionally specify a restricted set of channels,
+ * VLANs, and/or dMACs, in which it is interested.  By default, a
+ * given rule starts out matching all channels associated with the
+ * mPIPE context's set of open links; all VLANs; and all dMACs.
+ * Subsequent restrictions can then be added.
+ *
+ * @subsection mpipe__load_balancing Load Balancing
+ *
+ * The mPIPE load balancer is responsible for choosing the NotifRing
+ * to which the packet will be delivered.  This decision is based on
+ * the bucket number indicated by the classification program.  In
+ * general, the bucket number is based on some number of low bits of
+ * the packet's flow hash (applications that aren't interested in flow
+ * hashing use a single bucket).  Each load balancer bucket keeps a
+ * record of the NotifRing to which packets directed to that bucket
+ * are currently being delivered.  Based on the bucket's load
+ * balancing mode (@ref gxio_mpipe_bucket_mode_t), the load balancer
+ * either forwards the packet to the previously assigned NotifRing or
+ * decides to choose a new NotifRing.  If a new NotifRing is required,
+ * the load balancer chooses the least loaded ring in the NotifGroup
+ * associated with the bucket.
+ *
+ * The load balancer is a shared resource.  Each application needs to
+ * explicitly allocate NotifRings, NotifGroups, and buckets, using
+ * gxio_mpipe_alloc_notif_rings(), gxio_mpipe_alloc_notif_groups(),
+ * and gxio_mpipe_alloc_buckets().  Then the application needs to
+ * configure them using gxio_mpipe_init_notif_ring() and
+ * gxio_mpipe_init_notif_group_and_buckets().
+ *
+ * @subsection mpipe__buffers Buffer Selection and Packet Delivery
+ *
+ * Once the load balancer has chosen the destination NotifRing, the
+ * mPIPE DMA engine pops at least one buffer off of the 'buffer stack'
+ * chosen by the classification program and DMAs the packet data into
+ * that buffer.  Each buffer stack provides a hardware-accelerated
+ * stack of data buffers with the same size.  If the packet data is
+ * larger than the buffers provided by the chosen buffer stack, the
+ * mPIPE hardware pops off multiple buffers and chains the packet data
+ * through a multi-buffer linked list.  Once the packet data is
+ * delivered to the buffer(s), the mPIPE hardware writes the
+ * ::gxio_mpipe_idesc_t metadata object (calculated by the classifier)
+ * into the NotifRing and increments the number of packets delivered
+ * to that ring.
+ *
+ * Applications can push buffers onto a buffer stack by calling
+ * gxio_mpipe_push_buffer() or by egressing a packet with the
+ * ::gxio_mpipe_edesc_t::hwb bit set, indicating that the egressed
+ * buffers should be returned to the stack.
+ *
+ * Applications can allocate and initialize buffer stacks with the
+ * gxio_mpipe_alloc_buffer_stacks() and gxio_mpipe_init_buffer_stack()
+ * APIs.
+ *
+ * The application must also register the memory pages that will hold
+ * packets.  This requires calling gxio_mpipe_register_page() for each
+ * memory page that will hold packets allocated by the application for
+ * a given buffer stack.  Since each buffer stack is limited to 16
+ * registered pages, it may be necessary to use huge pages, or even
+ * extremely huge pages, to hold all the buffers.
+ *
+ * @subsection mpipe__iqueue NotifRings
+ *
+ * Each NotifRing is a region of shared memory, allocated by the
+ * application, to which the mPIPE delivers packet descriptors
+ * (::gxio_mpipe_idesc_t).  The application can allocate them via
+ * gxio_mpipe_alloc_notif_rings().  The application can then either
+ * explicitly initialize them with gxio_mpipe_init_notif_ring() and
+ * then read from them manually, or can make use of the convenience
+ * wrappers provided by @ref gxio_mpipe_wrappers.
+ *
+ * @section mpipe__egress mPIPE Egress Hardware
+ *
+ * Applications use eDMA rings to queue packets for egress.  The
+ * application can allocate them via gxio_mpipe_alloc_edma_rings().
+ * The application can then either explicitly initialize them with
+ * gxio_mpipe_init_edma_ring() and then write to them manually, or
+ * can make use of the convenience wrappers provided by
+ * @ref gxio_mpipe_wrappers.
+ *
+ * @section gxio__shortcomings Plans for Future API Revisions
+ *
+ * The API defined here is only an initial version of the mPIPE API.
+ * Future plans include:
+ *
+ * - Higher level wrapper functions to provide common initialization
+ * patterns.  This should help users start writing mPIPE programs
+ * without having to learn the details of the hardware.
+ *
+ * - Support for reset and deallocation of resources, including
+ * cleanup upon application shutdown.
+ *
+ * - Support for calling these APIs in the BME.
+ *
+ * - Support for IO interrupts.
+ *
+ * - Clearer definitions of thread safety guarantees.
+ *
+ * @section gxio__mpipe_examples Examples
+ *
+ * See the following mPIPE example programs for more information about
+ * allocating mPIPE resources and using them in real applications:
+ *
+ * - @ref mpipe/ingress/app.c : Receiving packets.
+ *
+ * - @ref mpipe/forward/app.c : Forwarding packets.
+ *
+ * Note that there are several more examples.
+ */
+
+/* Flags that can be passed to resource allocation functions. */
+enum gxio_mpipe_alloc_flags_e {
+	/* Require an allocation to start at a specified resource index. */
+	GXIO_MPIPE_ALLOC_FIXED = HV_MPIPE_ALLOC_FIXED,
+};
+
+/* Flags that can be passed to memory registration functions. */
+enum gxio_mpipe_mem_flags_e {
+	/* Do not fill L3 when writing, and invalidate lines upon egress. */
+	GXIO_MPIPE_MEM_FLAG_NT_HINT = IORPC_MEM_BUFFER_FLAG_NT_HINT,
+
+	/* L3 cache fills should only populate IO cache ways. */
+	GXIO_MPIPE_MEM_FLAG_IO_PIN = IORPC_MEM_BUFFER_FLAG_IO_PIN,
+};
+
+/* An ingress packet descriptor.  When a packet arrives, the mPIPE
+ * hardware generates this structure and writes it into a NotifRing.
+ */
+typedef MPIPE_PDESC_t gxio_mpipe_idesc_t;
+
+/* An egress command descriptor.  Applications write this structure
+ * into eDMA rings and the hardware performs the indicated operation
+ * (normally involving egressing some bytes).  Note that egressing a
+ * single packet may involve multiple egress command descriptors.
+ */
+typedef MPIPE_EDMA_DESC_t gxio_mpipe_edesc_t;
+
+/*
+ * Max # of mpipe instances. 2 currently.
+ */
+#define GXIO_MPIPE_INSTANCE_MAX  HV_MPIPE_INSTANCE_MAX
+
+#define NR_MPIPE_MAX   GXIO_MPIPE_INSTANCE_MAX
+
+/* Get the "va" field from an "idesc".
+ *
+ * This is the address at which the ingress hardware copied the first
+ * byte of the packet.
+ *
+ * If the classifier detected a custom header, then this will point to
+ * the custom header, and gxio_mpipe_idesc_get_l2_start() will point
+ * to the actual L2 header.
+ *
+ * Note that this value may be misleading if "idesc->be" is set.
+ *
+ * @param idesc An ingress packet descriptor.
+ */
+static inline unsigned char *gxio_mpipe_idesc_get_va(gxio_mpipe_idesc_t *idesc)
+{
+	return (unsigned char *)(long)idesc->va;
+}
+
+/* Get the "xfer_size" from an "idesc".
+ *
+ * This is the actual number of packet bytes transferred into memory
+ * by the hardware.
+ *
+ * Note that this value may be misleading if "idesc->be" is set.
+ *
+ * @param idesc An ingress packet descriptor.
+ *
+ * ISSUE: Is this the best name for this?
+ * FIXME: Add more docs about chaining, clipping, etc.
+ */
+static inline unsigned int gxio_mpipe_idesc_get_xfer_size(gxio_mpipe_idesc_t
+							  *idesc)
+{
+	return idesc->l2_size;
+}
+
+/* Get the "l2_offset" from an "idesc".
+ *
+ * Extremely customized classifiers might not support this function.
+ *
+ * This is the number of bytes between the "va" and the L2 header.
+ *
+ * The L2 header consists of a destination mac address, a source mac
+ * address, and an initial ethertype.  Various initial ethertypes
+ * allow encoding extra information in the L2 header, often including
+ * a vlan, and/or a new ethertype.
+ *
+ * Note that the "l2_offset" will be non-zero if (and only if) the
+ * classifier processed a custom header for the packet.
+ *
+ * @param idesc An ingress packet descriptor.
+ */
+static inline uint8_t gxio_mpipe_idesc_get_l2_offset(gxio_mpipe_idesc_t *idesc)
+{
+	return (idesc->custom1 >> 32) & 0xFF;
+}
+
+/* Get the "l2_start" from an "idesc".
+ *
+ * This is simply gxio_mpipe_idesc_get_va() plus
+ * gxio_mpipe_idesc_get_l2_offset().
+ *
+ * @param idesc An ingress packet descriptor.
+ */
+static inline unsigned char *gxio_mpipe_idesc_get_l2_start(gxio_mpipe_idesc_t
+							   *idesc)
+{
+	unsigned char *va = gxio_mpipe_idesc_get_va(idesc);
+	return va + gxio_mpipe_idesc_get_l2_offset(idesc);
+}
+
+/* Get the "l2_length" from an "idesc".
+ *
+ * This is simply gxio_mpipe_idesc_get_xfer_size() minus
+ * gxio_mpipe_idesc_get_l2_offset().
+ *
+ * @param idesc An ingress packet descriptor.
+ */
+static inline unsigned int gxio_mpipe_idesc_get_l2_length(gxio_mpipe_idesc_t
+							  *idesc)
+{
+	unsigned int xfer_size = idesc->l2_size;
+	return xfer_size - gxio_mpipe_idesc_get_l2_offset(idesc);
+}
+
+/* A context object used to manage mPIPE hardware resources. */
+typedef struct {
+
+	/* File descriptor for calling up to Linux (and thus the HV). */
+	int fd;
+
+	/* Corresponding mpipe instance #. */
+	int instance;
+
+	/* The VA at which configuration registers are mapped. */
+	char *mmio_cfg_base;
+
+	/* The VA at which IDMA, EDMA, and buffer manager are mapped. */
+	char *mmio_fast_base;
+
+	/* The "initialized" buffer stacks. */
+	gxio_mpipe_rules_stacks_t __stacks;
+
+} gxio_mpipe_context_t;
+
+/* This is only used internally, but it's most easily made visible here. */
+typedef gxio_mpipe_context_t gxio_mpipe_info_context_t;
+
+/* Initialize an mPIPE context.
+ *
+ * This function allocates an mPIPE "service domain" and maps the MMIO
+ * registers into the caller's VA space.
+ *
+ * @param context Context object to be initialized.
+ * @param mpipe_instance Instance number of mPIPE shim to be controlled via
+ *  context.
+ */
+extern int gxio_mpipe_init(gxio_mpipe_context_t *context,
+			   unsigned int mpipe_instance);
+
+/* Destroy an mPIPE context.
+ *
+ * This function frees the mPIPE "service domain" and unmaps the MMIO
+ * registers from the caller's VA space.
+ *
+ * If a user process exits without calling this routine, the kernel
+ * will destroy the mPIPE context as part of process teardown.
+ *
+ * @param context Context object to be destroyed.
+ */
+extern int gxio_mpipe_destroy(gxio_mpipe_context_t *context);
+
+/*****************************************************************
+ *                         Buffer Stacks                          *
+ ******************************************************************/
+
+/* Allocate a set of buffer stacks.
+ *
+ * The return value is NOT interesting if count is zero.
+ *
+ * @param context An initialized mPIPE context.
+ * @param count Number of stacks required.
+ * @param first Index of first stack if ::GXIO_MPIPE_ALLOC_FIXED flag is set,
+ *   otherwise ignored.
+ * @param flags Flag bits from ::gxio_mpipe_alloc_flags_e.
+ * @return Index of first allocated buffer stack, or
+ * ::GXIO_MPIPE_ERR_NO_BUFFER_STACK if allocation failed.
+ */
+extern int gxio_mpipe_alloc_buffer_stacks(gxio_mpipe_context_t *context,
+					  unsigned int count,
+					  unsigned int first,
+					  unsigned int flags);
+
+/* Enum codes for buffer sizes supported by mPIPE. */
+typedef enum {
+	/* 128 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_128 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_128,
+	/* 256 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_256 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_256,
+	/* 512 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_512 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_512,
+	/* 1024 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_1024 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_1024,
+	/* 1664 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_1664 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_1664,
+	/* 4096 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_4096 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_4096,
+	/* 10368 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_10368 =
+		MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_10368,
+	/* 16384 byte packet data buffer. */
+	GXIO_MPIPE_BUFFER_SIZE_16384 = MPIPE_BSM_INIT_DAT_1__SIZE_VAL_BSZ_16384
+} gxio_mpipe_buffer_size_enum_t;
+
+/* Convert a buffer size in bytes into a buffer size enum. */
+extern gxio_mpipe_buffer_size_enum_t
+gxio_mpipe_buffer_size_to_buffer_size_enum(size_t size);
+
+/* Convert a buffer size enum into a buffer size in bytes. */
+extern size_t
+gxio_mpipe_buffer_size_enum_to_buffer_size(gxio_mpipe_buffer_size_enum_t
+					   buffer_size_enum);
+
+/* Calculate the number of bytes required to store a given number of
+ * buffers in the memory registered with a buffer stack via
+ * gxio_mpipe_init_buffer_stack().
+ */
+extern size_t gxio_mpipe_calc_buffer_stack_bytes(unsigned long buffers);
+
+/* Initialize a buffer stack.  This function binds a region of memory
+ * to be used by the hardware for storing buffer addresses pushed via
+ * gxio_mpipe_push_buffer() or as the result of sending a buffer out
+ * the egress with the 'push to stack when done' bit set.  Once this
+ * function returns, the memory region's contents may be arbitrarily
+ * modified by the hardware at any time and software should not access
+ * the memory region again.
+ *
+ * @param context An initialized mPIPE context.
+ * @param stack The buffer stack index.
+ * @param buffer_size_enum The size of each buffer in the buffer stack,
+ * as an enum.
+ * @param mem The address of the buffer stack.  This memory must be
+ * physically contiguous and aligned to a 64kB boundary.
+ * @param mem_size The size of the buffer stack, in bytes.
+ * @param mem_flags ::gxio_mpipe_mem_flags_e memory flags.
+ * @return Zero on success, ::GXIO_MPIPE_ERR_INVAL_BUFFER_SIZE if
+ * buffer_size_enum is invalid, ::GXIO_MPIPE_ERR_BAD_BUFFER_STACK if
+ * stack has not been allocated.
+ */
+extern int gxio_mpipe_init_buffer_stack(gxio_mpipe_context_t *context,
+					unsigned int stack,
+					gxio_mpipe_buffer_size_enum_t
+					buffer_size_enum, void *mem,
+					size_t mem_size,
+					unsigned int mem_flags);
+
+/* Push a buffer onto a previously initialized buffer stack.
+ *
+ * The size of the buffer being pushed must match the size that was
+ * registered with gxio_mpipe_init_buffer_stack().  All packet buffer
+ * addresses are 128-byte aligned; the low 7 bits of the specified
+ * buffer address will be ignored.
+ *
+ * @param context An initialized mPIPE context.
+ * @param stack The buffer stack index.
+ * @param buffer The buffer (the low seven bits are ignored).
+ */
+static inline void gxio_mpipe_push_buffer(gxio_mpipe_context_t *context,
+					  unsigned int stack, void *buffer)
+{
+	MPIPE_BSM_REGION_ADDR_t offset = { {0} };
+	MPIPE_BSM_REGION_VAL_t val = { {0} };
+
+	/*
+	 * The mmio_fast_base region starts at the IDMA region, so subtract
+	 * off that initial offset.
+	 */
+	offset.region =
+		MPIPE_MMIO_ADDR__REGION_VAL_BSM -
+		MPIPE_MMIO_ADDR__REGION_VAL_IDMA;
+	offset.stack = stack;
+
+#if __SIZEOF_POINTER__ == 4
+	val.va = ((ulong) buffer) >> MPIPE_BSM_REGION_VAL__VA_SHIFT;
+#else
+	val.va = ((long)buffer) >> MPIPE_BSM_REGION_VAL__VA_SHIFT;
+#endif
+
+	__gxio_mmio_write(context->mmio_fast_base + offset.word, val.word);
+}
+
+/* Pop a buffer off of a previously initialized buffer stack.
+ *
+ * @param context An initialized mPIPE context.
+ * @param stack The buffer stack index.
+ * @return The buffer, or NULL if the stack is empty.
+ */
+static inline void *gxio_mpipe_pop_buffer(gxio_mpipe_context_t *context,
+					  unsigned int stack)
+{
+	MPIPE_BSM_REGION_ADDR_t offset = { {0} };
+
+	/*
+	 * The mmio_fast_base region starts at the IDMA region, so subtract
+	 * off that initial offset.
+	 */
+	offset.region =
+		MPIPE_MMIO_ADDR__REGION_VAL_BSM -
+		MPIPE_MMIO_ADDR__REGION_VAL_IDMA;
+	offset.stack = stack;
+
+	while (1) {
+		/*
+		 * Case 1: val.c == ..._UNCHAINED, va is non-zero.
+		 * Case 2: val.c == ..._INVALID, va is zero.
+		 * Case 3: val.c == ..._NOT_RDY, va is zero.
+		 */
+		MPIPE_BSM_REGION_VAL_t val;
+		val.word =
+			__gxio_mmio_read(context->mmio_fast_base +
+					 offset.word);
+
+		/*
+		 * Handle case 1 and 2 by returning the buffer (or NULL).
+		 * Handle case 3 by waiting for the prefetch buffer to refill.
+		 */
+		if (val.c != MPIPE_EDMA_DESC_WORD1__C_VAL_NOT_RDY)
+			return (void *)((unsigned long)val.
+					va << MPIPE_BSM_REGION_VAL__VA_SHIFT);
+	}
+}
+
+/*****************************************************************
+ *                          NotifRings                            *
+ ******************************************************************/
+
+/* Allocate a set of NotifRings.
+ *
+ * The return value is NOT interesting if count is zero.
+ *
+ * Note that NotifRings are allocated in chunks, so allocating one at
+ * a time is much less efficient than allocating several at once.
+ *
+ * @param context An initialized mPIPE context.
+ * @param count Number of NotifRings required.
+ * @param first Index of first NotifRing if ::GXIO_MPIPE_ALLOC_FIXED flag
+ *   is set, otherwise ignored.
+ * @param flags Flag bits from ::gxio_mpipe_alloc_flags_e.
+ * @return Index of first allocated buffer NotifRing, or
+ * ::GXIO_MPIPE_ERR_NO_NOTIF_RING if allocation failed.
+ */
+extern int gxio_mpipe_alloc_notif_rings(gxio_mpipe_context_t *context,
+					unsigned int count, unsigned int first,
+					unsigned int flags);
+
+/* Initialize a NotifRing, using the given memory and size.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ring The NotifRing index.
+ * @param mem A physically contiguous region of memory to be filled
+ * with a ring of ::gxio_mpipe_idesc_t structures.
+ * @param mem_size Number of bytes in the ring.  Must be 128, 512,
+ * 2048, or 65536 * sizeof(gxio_mpipe_idesc_t).
+ * @param mem_flags ::gxio_mpipe_mem_flags_e memory flags.
+ *
+ * @return 0 on success, ::GXIO_MPIPE_ERR_BAD_NOTIF_RING or
+ * ::GXIO_ERR_INVAL_MEMORY_SIZE on failure.
+ */
+extern int gxio_mpipe_init_notif_ring(gxio_mpipe_context_t *context,
+				      unsigned int ring,
+				      void *mem, size_t mem_size,
+				      unsigned int mem_flags);
+
+/* Configure an interrupt to be sent to a tile on incoming NotifRing
+ *  traffic.  Once an interrupt is sent for a particular ring, no more
+ *  will be sent until gxio_mica_enable_notif_ring_interrupt() is called.
+ *
+ * @param context An initialized mPIPE context.
+ * @param x X coordinate of interrupt target tile.
+ * @param y Y coordinate of interrupt target tile.
+ * @param i Index of the IPI register which will receive the interrupt.
+ * @param e Specific event which will be set in the target IPI register when
+ * the interrupt occurs.
+ * @param ring The NotifRing index.
+ * @return Zero on success, GXIO_ERR_INVAL if params are out of range.
+ */
+extern int gxio_mpipe_request_notif_ring_interrupt(gxio_mpipe_context_t
+						   *context, int x, int y,
+						   int i, int e,
+						   unsigned int ring);
+
+/* Enable an interrupt on incoming NotifRing traffic.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ring The NotifRing index.
+ * @return Zero on success, GXIO_ERR_INVAL if params are out of range.
+ */
+extern int gxio_mpipe_enable_notif_ring_interrupt(gxio_mpipe_context_t
+						  *context, unsigned int ring);
+
+/* Map all of a client's memory via the given IOTLB.
+ * @param context An initialized mPIPE context.
+ * @param iotlb IOTLB index.
+ * @param pte Page table entry.
+ * @param flags Flags.
+ * @return Zero on success, or a negative error code.
+ */
+extern int gxio_mpipe_register_client_memory(gxio_mpipe_context_t *context,
+					     unsigned int iotlb, HV_PTE pte,
+					     unsigned int flags);
+
+/*****************************************************************
+ *                        Notif Groups                            *
+ ******************************************************************/
+
+/* Allocate a set of NotifGroups.
+ *
+ * The return value is NOT interesting if count is zero.
+ *
+ * @param context An initialized mPIPE context.
+ * @param count Number of NotifGroups required.
+ * @param first Index of first NotifGroup if ::GXIO_MPIPE_ALLOC_FIXED flag
+ *   is set, otherwise ignored.
+ * @param flags Flag bits from ::gxio_mpipe_alloc_flags_e.
+ * @return Index of first allocated buffer NotifGroup, or
+ * ::GXIO_MPIPE_ERR_NO_NOTIF_GROUP if allocation failed.
+ */
+extern int gxio_mpipe_alloc_notif_groups(gxio_mpipe_context_t *context,
+					 unsigned int count,
+					 unsigned int first,
+					 unsigned int flags);
+
+/* Add a NotifRing to a NotifGroup.  This only sets a bit in the
+ * application's 'group' object; the hardware NotifGroup can be
+ * initialized by passing 'group' to gxio_mpipe_init_notif_group() or
+ * gxio_mpipe_init_notif_group_and_buckets().
+ */
+static inline void
+gxio_mpipe_notif_group_add_ring(gxio_mpipe_notif_group_bits_t *bits, int ring)
+{
+	bits->ring_mask[ring / 64] |= (1ull << (ring % 64));
+}
+
+/* Set a particular NotifGroup bitmask.  Since the load balancer
+ * makes decisions based on both bucket and NotifGroup state, most
+ * applications should use gxio_mpipe_init_notif_group_and_buckets()
+ * rather than using this function to configure just a NotifGroup.
+ */
+extern int gxio_mpipe_init_notif_group(gxio_mpipe_context_t *context,
+				       unsigned int group,
+				       gxio_mpipe_notif_group_bits_t bits);
+
+/*****************************************************************
+ *                         Load Balancer                          *
+ ******************************************************************/
+
+/* Allocate a set of load balancer buckets.
+ *
+ * The return value is NOT interesting if count is zero.
+ *
+ * Note that buckets are allocated in chunks, so allocating one at
+ * a time is much less efficient than allocating several at once.
+ *
+ * Note that the buckets are actually divided into two sub-ranges, of
+ * different sizes, and different chunk sizes, and the range you get
+ * by default is determined by the size of the request.  Allocations
+ * cannot span the two sub-ranges.
+ *
+ * @param context An initialized mPIPE context.
+ * @param count Number of buckets required.
+ * @param first Index of first bucket if ::GXIO_MPIPE_ALLOC_FIXED flag is set,
+ *   otherwise ignored.
+ * @param flags Flag bits from ::gxio_mpipe_alloc_flags_e.
+ * @return Index of first allocated buffer bucket, or
+ * ::GXIO_MPIPE_ERR_NO_BUCKET if allocation failed.
+ */
+extern int gxio_mpipe_alloc_buckets(gxio_mpipe_context_t *context,
+				    unsigned int count, unsigned int first,
+				    unsigned int flags);
+
+/* The legal modes for gxio_mpipe_bucket_info_t and
+ * gxio_mpipe_init_notif_group_and_buckets().
+ *
+ * All modes except ::GXIO_MPIPE_BUCKET_ROUND_ROBIN expect that the user
+ * will allocate a power-of-two number of buckets and initialize them
+ * to the same mode.  The classifier program then uses the appropriate
+ * number of low bits from the incoming packet's flow hash to choose a
+ * load balancer bucket.  Based on that bucket's load balancing mode,
+ * reference count, and currently active NotifRing, the load balancer
+ * chooses the NotifRing to which the packet will be delivered.
+ */
+typedef enum {
+	/* All packets for a bucket go to the same NotifRing unless the
+	 * NotifRing gets full, in which case packets will be dropped.  If
+	 * the bucket reference count ever reaches zero, a new NotifRing may
+	 * be chosen.
+	 */
+	GXIO_MPIPE_BUCKET_DYNAMIC_FLOW_AFFINITY =
+		MPIPE_LBL_INIT_DAT_BSTS_TBL__MODE_VAL_DFA,
+
+	/* All packets for a bucket always go to the same NotifRing.
+	 */
+	GXIO_MPIPE_BUCKET_STATIC_FLOW_AFFINITY =
+		MPIPE_LBL_INIT_DAT_BSTS_TBL__MODE_VAL_FIXED,
+
+	/* All packets for a bucket go to the least full NotifRing in the
+	 * group, providing load balancing round robin behavior.
+	 */
+	GXIO_MPIPE_BUCKET_ROUND_ROBIN =
+		MPIPE_LBL_INIT_DAT_BSTS_TBL__MODE_VAL_ALWAYS_PICK,
+
+	/* All packets for a bucket go to the same NotifRing unless the
+	 * NotifRing gets full, at which point the bucket starts using the
+	 * least full NotifRing in the group.  If all NotifRings in the
+	 * group are full, packets will be dropped.
+	 */
+	GXIO_MPIPE_BUCKET_STICKY_FLOW_LOCALITY =
+		MPIPE_LBL_INIT_DAT_BSTS_TBL__MODE_VAL_STICKY,
+
+	/* All packets for a bucket go to the same NotifRing unless the
+	 * NotifRing gets full, or a random timer fires, at which point the
+	 * bucket starts using the least full NotifRing in the group.  If
+	 * all NotifRings in the group are full, packets will be dropped.
+	 * WARNING: This mode is BROKEN on chips with fewer than 64 tiles.
+	 */
+	GXIO_MPIPE_BUCKET_PREFER_FLOW_LOCALITY =
+		MPIPE_LBL_INIT_DAT_BSTS_TBL__MODE_VAL_STICKY_RAND,
+
+} gxio_mpipe_bucket_mode_t;
+
+/* Copy a set of bucket initialization values into the mPIPE
+ * hardware.  Since the load balancer makes decisions based on both
+ * bucket and NotifGroup state, most applications should use
+ * gxio_mpipe_init_notif_group_and_buckets() rather than using this
+ * function to configure a single bucket.
+ *
+ * @param context An initialized mPIPE context.
+ * @param bucket Bucket index to be initialized.
+ * @param bucket_info Initial reference count, NotifRing index, and mode.
+ * @return 0 on success, ::GXIO_MPIPE_ERR_BAD_BUCKET on failure.
+ */
+extern int gxio_mpipe_init_bucket(gxio_mpipe_context_t *context,
+				  unsigned int bucket,
+				  gxio_mpipe_bucket_info_t bucket_info);
+
+/* Initializes a group and range of buckets and range of rings such
+ * that the load balancer runs a particular load balancing function.
+ *
+ * First, the group is initialized with the given rings.
+ *
+ * Second, each bucket is initialized with the mode and group, and a
+ * ring chosen round-robin from the given rings.
+ *
+ * Normally, the classifier picks a bucket, and then the load balancer
+ * picks a ring, based on the bucket's mode, group, and current ring,
+ * possibly updating the bucket's ring.
+ *
+ * @param context An initialized mPIPE context.
+ * @param group The group.
+ * @param ring The first ring.
+ * @param num_rings The number of rings.
+ * @param bucket The first bucket.
+ * @param num_buckets The number of buckets.
+ * @param mode The load balancing mode.
+ *
+ * @return 0 on success, ::GXIO_MPIPE_ERR_BAD_BUCKET,
+ * ::GXIO_MPIPE_ERR_BAD_NOTIF_GROUP, or
+ * ::GXIO_MPIPE_ERR_BAD_NOTIF_RING on failure.
+ */
+extern int gxio_mpipe_init_notif_group_and_buckets(gxio_mpipe_context_t
+						   *context,
+						   unsigned int group,
+						   unsigned int ring,
+						   unsigned int num_rings,
+						   unsigned int bucket,
+						   unsigned int num_buckets,
+						   gxio_mpipe_bucket_mode_t
+						   mode);
+
+/* Return credits to a NotifRing and/or bucket.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ring The NotifRing index, or -1.
+ * @param bucket The bucket, or -1.
+ * @param count The number of credits to return.
+ */
+static inline void gxio_mpipe_credit(gxio_mpipe_context_t *context,
+				     int ring, int bucket, unsigned int count)
+{
+	/* NOTE: Fancy struct initialization would break "C89" header test. */
+
+	MPIPE_IDMA_RELEASE_REGION_ADDR_t offset = { {0} };
+	MPIPE_IDMA_RELEASE_REGION_VAL_t val = { {0} };
+
+	/*
+	 * The mmio_fast_base region starts at the IDMA region, so subtract
+	 * off that initial offset.
+	 */
+	offset.region =
+		MPIPE_MMIO_ADDR__REGION_VAL_IDMA -
+		MPIPE_MMIO_ADDR__REGION_VAL_IDMA;
+	offset.ring = ring;
+	offset.bucket = bucket;
+	offset.ring_enable = (ring >= 0);
+	offset.bucket_enable = (bucket >= 0);
+	val.count = count;
+
+	__gxio_mmio_write(context->mmio_fast_base + offset.word, val.word);
+}
+
+/*****************************************************************
+ *                         Egress Rings                           *
+ ******************************************************************/
+
+/* Allocate a set of eDMA rings.
+ *
+ * The return value is NOT interesting if count is zero.
+ *
+ * @param context An initialized mPIPE context.
+ * @param count Number of eDMA rings required.
+ * @param first Index of first eDMA ring if ::GXIO_MPIPE_ALLOC_FIXED flag
+ *   is set, otherwise ignored.
+ * @param flags Flag bits from ::gxio_mpipe_alloc_flags_e.
+ * @return Index of first allocated buffer eDMA ring, or
+ * ::GXIO_MPIPE_ERR_NO_EDMA_RING if allocation failed.
+ */
+extern int gxio_mpipe_alloc_edma_rings(gxio_mpipe_context_t *context,
+				       unsigned int count, unsigned int first,
+				       unsigned int flags);
+
+/* Initialize an eDMA ring, using the given memory and size.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ering The eDMA ring index.
+ * @param channel The channel to use.  This must be one of the channels
+ * associated with the context's set of open links.
+ * @param mem A physically contiguous region of memory to be filled
+ * with a ring of ::gxio_mpipe_edesc_t structures.
+ * @param mem_size Number of bytes in the ring.  Must be 512, 2048,
+ * 8192 or 65536, times 16 (i.e. sizeof(gxio_mpipe_edesc_t)).
+ * @param mem_flags ::gxio_mpipe_mem_flags_e memory flags.
+ *
+ * @return 0 on success, ::GXIO_MPIPE_ERR_BAD_EDMA_RING or
+ * ::GXIO_ERR_INVAL_MEMORY_SIZE on failure.
+ */
+extern int gxio_mpipe_init_edma_ring(gxio_mpipe_context_t *context,
+				     unsigned int ering, unsigned int channel,
+				     void *mem, size_t mem_size,
+				     unsigned int mem_flags);
+
+/* Set the "max_blks", "min_snf_blks", and "db" fields of
+ * ::MPIPE_EDMA_RG_INIT_DAT_THRESH_t for a given edma ring.
+ *
+ * The global pool of dynamic blocks will be automatically adjusted.
+ *
+ * This function should not be called after any egress has been done
+ * on the edma ring.
+ *
+ * Most applications should just use gxio_mpipe_equeue_set_snf_size().
+ *
+ * @param context An initialized mPIPE context.
+ * @param ering The eDMA ring index.
+ * @param max_blks The number of blocks to dedicate to the ring
+ * (normally min_snf_blks + 1).  Must be greater than min_snf_blocks.
+ * @param min_snf_blks The number of blocks which must be stored
+ * prior to starting to send the packet (normally 12).
+ * @param db Whether to allow use of dynamic blocks by the ring
+ * (normally 1).
+ *
+ * @return 0 on success, negative on error.
+ */
+extern int gxio_mpipe_config_edma_ring_blks(gxio_mpipe_context_t *context,
+					    unsigned int ering,
+					    unsigned int max_blks,
+					    unsigned int min_snf_blks,
+					    unsigned int db);
+
+/*****************************************************************
+ *                      Classifier Program                        *
+ ******************************************************************/
+
+/*
+ *
+ * Functions for loading or configuring the mPIPE classifier program.
+ *
+ * The mPIPE classification processors all run a special "classifier"
+ * program which, for each incoming packet, parses the packet headers,
+ * encodes some packet metadata in the "idesc", and either drops the
+ * packet, or picks a notif ring to handle the packet, and a buffer
+ * stack to contain the packet, usually based on the channel, VLAN,
+ * dMAC, flow hash, and packet size, under the guidance of the "rules"
+ * API described below.
+ *
+ * @section gxio_mpipe_classifier_default Default Classifier
+ *
+ * The MDE provides a simple "default" classifier program.  It is
+ * shipped as source in "$TILERA_ROOT/src/sys/mpipe/classifier.c",
+ * which serves as its official documentation.  It is shipped as a
+ * binary program in "$TILERA_ROOT/tile/boot/classifier", which is
+ * automatically included in bootroms created by "tile-monitor", and
+ * is automatically loaded by the hypervisor at boot time.
+ *
+ * The L2 analysis handles LLC packets, SNAP packets, and "VLAN
+ * wrappers" (keeping the outer VLAN).
+ *
+ * The L3 analysis handles IPv4 and IPv6, dropping packets with bad
+ * IPv4 header checksums, requesting computation of a TCP/UDP checksum
+ * if appropriate, and hashing the dest and src IP addresses, plus the
+ * ports for TCP/UDP packets, into the flow hash.  No special analysis
+ * is done for "fragmented" packets or "tunneling" protocols.  Thus,
+ * the first fragment of a fragmented TCP/UDP packet is hashed using
+ * src/dest IP address and ports and all subsequent fragments are only
+ * hashed according to src/dest IP address.
+ *
+ * The L3 analysis handles other packets too, hashing the dMAC
+ * smac into a flow hash.
+ *
+ * The channel, VLAN, and dMAC used to pick a "rule" (see the
+ * "rules" APIs below), which in turn is used to pick a buffer stack
+ * (based on the packet size) and a bucket (based on the flow hash).
+ *
+ * To receive traffic matching a particular (channel/VLAN/dMAC
+ * pattern, an application should allocate its own buffer stacks and
+ * load balancer buckets, and map traffic to those stacks and buckets,
+ * as decribed by the "rules" API below.
+ *
+ * Various packet metadata is encoded in the idesc.  The flow hash is
+ * four bytes at 0x0C.  The VLAN is two bytes at 0x10.  The ethtype is
+ * two bytes at 0x12.  The l3 start is one byte at 0x14.  The l4 start
+ * is one byte at 0x15 for IPv4 and IPv6 packets, and otherwise zero.
+ * The protocol is one byte at 0x16 for IPv4 and IPv6 packets, and
+ * otherwise zero.
+ *
+ * @section gxio_mpipe_classifier_custom Custom Classifiers.
+ *
+ * A custom classifier may be created using "tile-mpipe-cc" with a
+ * customized version of the default classifier sources.
+ *
+ * The custom classifier may be included in bootroms using the
+ * "--classifier" option to "tile-monitor", or loaded dynamically
+ * using gxio_mpipe_classifier_load_from_file().
+ *
+ * Be aware that "extreme" customizations may break the assumptions of
+ * the "rules" APIs described below, but simple customizations, such
+ * as adding new packet metadata, should be fine.
+ */
+
+/* A set of classifier rules, plus a context. */
+typedef struct {
+
+	/* The context. */
+	gxio_mpipe_context_t *context;
+
+	/* The actual rules. */
+	gxio_mpipe_rules_list_t list;
+
+} gxio_mpipe_rules_t;
+
+/* Initialize a classifier program rules list.
+ *
+ * This function can be called on a previously initialized rules list
+ * to discard any previously added rules.
+ *
+ * @param rules Rules list to initialize.
+ * @param context An initialized mPIPE context.
+ */
+extern void gxio_mpipe_rules_init(gxio_mpipe_rules_t *rules,
+				  gxio_mpipe_context_t *context);
+
+/* Begin a new rule on the indicated rules list.
+ *
+ * Note that an empty rule matches all packets, but an empty rule list
+ * matches no packets.
+ *
+ * @param rules Rules list to which new rule is appended.
+ * @param bucket First load balancer bucket to which packets will be
+ * delivered.
+ * @param num_buckets Number of buckets (must be a power of two) across
+ * which packets will be distributed based on the "flow hash".
+ * @param stacks Either NULL, to assign each packet to the smallest
+ * initialized buffer stack which does not induce chaining (and to
+ * drop packets which exceed the largest initialized buffer stack
+ * buffer size), or an array, with each entry indicating which buffer
+ * stack should be used for packets up to that size (with 255
+ * indicating that those packets should be dropped).
+ * @return 0 on success, or a negative error code on failure.
+ */
+extern int gxio_mpipe_rules_begin(gxio_mpipe_rules_t *rules,
+				  unsigned int bucket,
+				  unsigned int num_buckets,
+				  gxio_mpipe_rules_stacks_t *stacks);
+
+/* Set the headroom of the current rule.
+ *
+ * @param rules Rules list whose current rule will be modified.
+ * @param headroom The headroom.
+ * @return 0 on success, or a negative error code on failure.
+ */
+extern int gxio_mpipe_rules_set_headroom(gxio_mpipe_rules_t *rules,
+					 uint8_t headroom);
+
+/* Indicate that packets from a particular channel can be delivered
+ * to the buckets and buffer stacks associated with the current rule.
+ *
+ * Channels added must be associated with links opened by the mPIPE context
+ * used in gxio_mpipe_rules_init().  A rule with no channels is equivalent
+ * to a rule naming all such associated channels.
+ *
+ * @param rules Rules list whose current rule will be modified.
+ * @param channel The channel to add.
+ * @return 0 on success, or a negative error code on failure.
+ */
+extern int gxio_mpipe_rules_add_channel(gxio_mpipe_rules_t *rules,
+					unsigned int channel);
+
+/* Commit rules.
+ *
+ * The rules are sent to the hypervisor, where they are combined with
+ * the rules from other apps, and used to program the hardware classifier.
+ *
+ * Note that if this function returns an error, then the rules will NOT
+ * have been committed, even if the error is due to interactions with
+ * rules from another app.
+ *
+ * @param rules Rules list to commit.
+ * @return 0 on success, or a negative error code on failure.
+ */
+extern int gxio_mpipe_rules_commit(gxio_mpipe_rules_t *rules);
+
+/*****************************************************************
+ *                     Ingress Queue Wrapper                      *
+ ******************************************************************/
+
+/*
+ *
+ * Convenience functions for receiving packets from a NotifRing and
+ * sending packets via an eDMA ring.
+ *
+ * The mpipe ingress and egress hardware uses shared memory packet
+ * descriptors to describe packets that have arrived on ingress or
+ * are destined for egress.  These descriptors are stored in shared
+ * memory ring buffers and written or read by hardware as necessary.
+ * The gxio library provides wrapper functions that manage the head and
+ * tail pointers for these rings, allowing the user to easily read or
+ * write packet descriptors.
+ *
+ * The initialization interface for ingress and egress rings is quite
+ * similar.  For example, to create an ingress queue, the user passes
+ * a ::gxio_mpipe_iqueue_t state object, a ring number from
+ * gxio_mpipe_alloc_notif_rings(), and the address of memory to hold a
+ * ring buffer to the gxio_mpipe_iqueue_init() function.  The function
+ * returns success when the state object has been initialized and the
+ * hardware configured to deliver packets to the specified ring
+ * buffer.  Similarly, gxio_mpipe_equeue_init() takes a
+ * ::gxio_mpipe_equeue_t state object, a ring number from
+ * gxio_mpipe_alloc_edma_rings(), and a shared memory buffer.
+ *
+ * @section gxio_mpipe_iqueue Working with Ingress Queues
+ *
+ * Once initialized, the gxio_mpipe_iqueue_t API provides two flows
+ * for getting the ::gxio_mpipe_idesc_t packet descriptor associated
+ * with incoming packets.  The simplest is to call
+ * gxio_mpipe_iqueue_get() or gxio_mpipe_iqueue_try_get().  These
+ * functions copy the oldest packet descriptor out of the NotifRing and
+ * into a descriptor provided by the caller.  They also immediately
+ * inform the hardware that a descriptor has been processed.
+ *
+ * For applications with stringent performance requirements, higher
+ * efficiency can be achieved by avoiding the packet descriptor copy
+ * and processing multiple descriptors at once.  The
+ * gxio_mpipe_iqueue_peek() and gxio_mpipe_iqueue_try_peek() functions
+ * allow such optimizations.  These functions provide a pointer to the
+ * next valid ingress descriptor in the NotifRing's shared memory ring
+ * buffer, and a count of how many contiguous descriptors are ready to
+ * be processed.  The application can then process any number of those
+ * descriptors in place, calling gxio_mpipe_iqueue_consume() to inform
+ * the hardware after each one has been processed.
+ *
+ * @section gxio_mpipe_equeue Working with Egress Queues
+ *
+ * Similarly, the egress queue API provides a high-performance
+ * interface plus a simple wrapper for use in posting
+ * ::gxio_mpipe_edesc_t egress packet descriptors.  The simple
+ * version, gxio_mpipe_equeue_put(), allows the programmer to wait for
+ * an eDMA ring slot to become available and write a single descriptor
+ * into the ring.
+ *
+ * Alternatively, you can reserve slots in the eDMA ring using
+ * gxio_mpipe_equeue_reserve() or gxio_mpipe_equeue_try_reserve(), and
+ * then fill in each slot using gxio_mpipe_equeue_put_at().  This
+ * capability can be used to amortize the cost of reserving slots
+ * across several packets.  It also allows gather operations to be
+ * performed on a shared equeue, by ensuring that the edescs for all
+ * the fragments are all contiguous in the eDMA ring.
+ *
+ * The gxio_mpipe_equeue_reserve() and gxio_mpipe_equeue_try_reserve()
+ * functions return a 63-bit "completion slot", which is actually a
+ * sequence number, the low bits of which indicate the ring buffer
+ * index and the high bits the number of times the application has
+ * gone around the egress ring buffer.  The extra bits allow an
+ * application to check for egress completion by calling
+ * gxio_mpipe_equeue_is_complete() to see whether a particular 'slot'
+ * number has finished.  Given the maximum packet rates of the Gx
+ * processor, the 63-bit slot number will never wrap.
+ *
+ * In practice, most applications use the ::gxio_mpipe_edesc_t::hwb
+ * bit to indicate that the buffers containing egress packet data
+ * should be pushed onto a buffer stack when egress is complete.  Such
+ * applications generally do not need to know when an egress operation
+ * completes (since there is no need to free a buffer post-egress),
+ * and thus can use the optimized gxio_mpipe_equeue_reserve_fast() or
+ * gxio_mpipe_equeue_try_reserve_fast() functions, which return a 24
+ * bit "slot", instead of a 63-bit "completion slot".
+ *
+ * Once a slot has been "reserved", it MUST be filled.  If the
+ * application reserves a slot and then decides that it does not
+ * actually need it, it can set the ::gxio_mpipe_edesc_t::ns (no send)
+ * bit on the descriptor passed to gxio_mpipe_equeue_put_at() to
+ * indicate that no data should be sent.  This technique can also be
+ * used to drop an incoming packet, instead of forwarding it, since
+ * any buffer will still be pushed onto the buffer stack when the
+ * egress descriptor is processed.
+ */
+
+/* A convenient interface to a NotifRing, for use by a single thread.
+ */
+typedef struct {
+
+	/* The context. */
+	gxio_mpipe_context_t *context;
+
+	/* The actual NotifRing. */
+	gxio_mpipe_idesc_t *idescs;
+
+	/* The number of entries. */
+	unsigned long num_entries;
+
+	/* The number of entries minus one. */
+	unsigned long mask_num_entries;
+
+	/* The log2() of the number of entries. */
+	unsigned long log2_num_entries;
+
+	/* The next entry. */
+	unsigned int head;
+
+	/* The NotifRing id. */
+	unsigned int ring;
+
+#ifdef __BIG_ENDIAN__
+	/* The number of byteswapped entries. */
+	unsigned int swapped;
+#endif
+
+} gxio_mpipe_iqueue_t;
+
+/* Initialize an "iqueue".
+ *
+ * Takes the iqueue plus the same args as gxio_mpipe_init_notif_ring().
+ */
+extern int gxio_mpipe_iqueue_init(gxio_mpipe_iqueue_t *iqueue,
+				  gxio_mpipe_context_t *context,
+				  unsigned int ring,
+				  void *mem, size_t mem_size,
+				  unsigned int mem_flags);
+
+/* Advance over some old entries in an iqueue.
+ *
+ * Please see the documentation for gxio_mpipe_iqueue_consume().
+ *
+ * @param iqueue An ingress queue initialized via gxio_mpipe_iqueue_init().
+ * @param count The number of entries to advance over.
+ */
+static inline void gxio_mpipe_iqueue_advance(gxio_mpipe_iqueue_t *iqueue,
+					     int count)
+{
+	/* Advance with proper wrap. */
+	int head = iqueue->head + count;
+	iqueue->head =
+		(head & iqueue->mask_num_entries) +
+		(head >> iqueue->log2_num_entries);
+
+#ifdef __BIG_ENDIAN__
+	/* HACK: Track swapped entries. */
+	iqueue->swapped -= count;
+#endif
+}
+
+/* Release the ring and bucket for an old entry in an iqueue.
+ *
+ * Releasing the ring allows more packets to be delivered to the ring.
+ *
+ * Releasing the bucket allows flows using the bucket to be moved to a
+ * new ring when using GXIO_MPIPE_BUCKET_DYNAMIC_FLOW_AFFINITY.
+ *
+ * This function is shorthand for "gxio_mpipe_credit(iqueue->context,
+ * iqueue->ring, idesc->bucket_id, 1)", and it may be more convenient
+ * to make that underlying call, using those values, instead of
+ * tracking the entire "idesc".
+ *
+ * If packet processing is deferred, optimal performance requires that
+ * the releasing be deferred as well.
+ *
+ * Please see the documentation for gxio_mpipe_iqueue_consume().
+ *
+ * @param iqueue An ingress queue initialized via gxio_mpipe_iqueue_init().
+ * @param idesc The descriptor which was processed.
+ */
+static inline void gxio_mpipe_iqueue_release(gxio_mpipe_iqueue_t *iqueue,
+					     gxio_mpipe_idesc_t *idesc)
+{
+	gxio_mpipe_credit(iqueue->context, iqueue->ring, idesc->bucket_id, 1);
+}
+
+/* Consume a packet from an "iqueue".
+ *
+ * After processing packets peeked at via gxio_mpipe_iqueue_peek()
+ * or gxio_mpipe_iqueue_try_peek(), you must call this function, or
+ * gxio_mpipe_iqueue_advance() plus gxio_mpipe_iqueue_release(), to
+ * advance over those entries, and release their rings and buckets.
+ *
+ * You may call this function as each packet is processed, or you can
+ * wait until several packets have been processed.
+ *
+ * Note that if you are using a single bucket, and you are handling
+ * batches of N packets, then you can replace several calls to this
+ * function with calls to "gxio_mpipe_iqueue_advance(iqueue, N)" and
+ * "gxio_mpipe_credit(iqueue->context, iqueue->ring, bucket, N)".
+ *
+ * Note that if your classifier sets "idesc->nr", then you should
+ * explicitly call "gxio_mpipe_iqueue_advance(iqueue, idesc)" plus
+ * "gxio_mpipe_credit(iqueue->context, iqueue->ring, -1, 1)", to
+ * avoid incorrectly crediting the (unused) bucket.
+ *
+ * @param iqueue An ingress queue initialized via gxio_mpipe_iqueue_init().
+ * @param idesc The descriptor which was processed.
+ */
+static inline void gxio_mpipe_iqueue_consume(gxio_mpipe_iqueue_t *iqueue,
+					     gxio_mpipe_idesc_t *idesc)
+{
+	gxio_mpipe_iqueue_advance(iqueue, 1);
+	gxio_mpipe_iqueue_release(iqueue, idesc);
+}
+
+/* Peek at the next packet(s) in an "iqueue", without waiting.
+ *
+ * If no packets are available, fills idesc_ref with NULL, and then
+ * returns ::GXIO_MPIPE_ERR_IQUEUE_EMPTY.  Otherwise, fills idesc_ref
+ * with the address of the next valid packet descriptor, and returns
+ * the maximum number of valid descriptors which can be processed.
+ * You may process fewer descriptors if desired.
+ *
+ * Call gxio_mpipe_iqueue_consume() on each packet once it has been
+ * processed (or dropped), to allow more packets to be delivered.
+ *
+ * @param iqueue An ingress queue initialized via gxio_mpipe_iqueue_init().
+ * @param idesc_ref A pointer to a packet descriptor pointer.
+ * @return The (positive) number of packets which can be processed,
+ * or ::GXIO_MPIPE_ERR_IQUEUE_EMPTY if no packets are available.
+ */
+static inline int gxio_mpipe_iqueue_try_peek(gxio_mpipe_iqueue_t *iqueue,
+					     gxio_mpipe_idesc_t **idesc_ref)
+{
+	gxio_mpipe_idesc_t *next;
+
+	uint64_t head = iqueue->head;
+	uint64_t tail = __gxio_mmio_read(iqueue->idescs);
+
+	/* Available entries. */
+	uint64_t avail =
+		(tail >= head) ? (tail - head) : (iqueue->num_entries - head);
+
+	if (avail == 0) {
+		*idesc_ref = NULL;
+		return GXIO_MPIPE_ERR_IQUEUE_EMPTY;
+	}
+
+	next = &iqueue->idescs[head];
+
+	/* ISSUE: Is this helpful? */
+	__insn_prefetch(next);
+
+#ifdef __BIG_ENDIAN__
+	/* HACK: Swap new entries directly in memory. */
+	{
+		int i, j;
+		for (i = iqueue->swapped; i < avail; i++) {
+			for (j = 0; j < 8; j++)
+				next[i].words[j] =
+					__builtin_bswap64(next[i].words[j]);
+		}
+		iqueue->swapped = avail;
+	}
+#endif
+
+	*idesc_ref = next;
+
+	return avail;
+}
+
+/* Drop a packet by pushing its buffer (if appropriate).
+ *
+ * NOTE: The caller must still call gxio_mpipe_iqueue_consume() if idesc
+ * came from gxio_mpipe_iqueue_try_peek() or gxio_mpipe_iqueue_peek().
+ *
+ * @param iqueue An ingress queue initialized via gxio_mpipe_iqueue_init().
+ * @param idesc A packet descriptor.
+ */
+static inline void gxio_mpipe_iqueue_drop(gxio_mpipe_iqueue_t *iqueue,
+					  gxio_mpipe_idesc_t *idesc)
+{
+	/* FIXME: Handle "chaining" properly. */
+
+	if (!idesc->be) {
+		unsigned char *va = gxio_mpipe_idesc_get_va(idesc);
+		gxio_mpipe_push_buffer(iqueue->context, idesc->stack_idx, va);
+	}
+}
+
+/*****************************************************************
+ *                      Egress Queue Wrapper                      *
+ ******************************************************************/
+
+/* A convenient, thread-safe interface to an eDMA ring. */
+typedef struct {
+
+	/* State object for tracking head and tail pointers. */
+	__gxio_dma_queue_t dma_queue;
+
+	/* The ring entries. */
+	gxio_mpipe_edesc_t *edescs;
+
+	/* The number of entries minus one. */
+	unsigned long mask_num_entries;
+
+	/* The log2() of the number of entries. */
+	unsigned long log2_num_entries;
+
+	/* The context. */
+	gxio_mpipe_context_t *context;
+
+	/* The ering. */
+	unsigned int ering;
+
+	/* The channel. */
+	unsigned int channel;
+
+} gxio_mpipe_equeue_t;
+
+/* Initialize an "equeue".
+ *
+ * This function uses gxio_mpipe_init_edma_ring() to initialize the
+ * underlying edma_ring using the provided arguments.
+ *
+ * @param equeue An egress queue to be initialized.
+ * @param context An initialized mPIPE context.
+ * @param ering The eDMA ring index.
+ * @param channel The channel to use.  This must be one of the channels
+ * associated with the context's set of open links.
+ * @param mem A physically contiguous region of memory to be filled
+ * with a ring of ::gxio_mpipe_edesc_t structures.
+ * @param mem_size Number of bytes in the ring.  Must be 512, 2048,
+ * 8192 or 65536, times 16 (i.e. sizeof(gxio_mpipe_edesc_t)).
+ * @param mem_flags ::gxio_mpipe_mem_flags_e memory flags.
+ *
+ * @return 0 on success, ::GXIO_MPIPE_ERR_BAD_EDMA_RING or
+ * ::GXIO_ERR_INVAL_MEMORY_SIZE on failure.
+ */
+extern int gxio_mpipe_equeue_init(gxio_mpipe_equeue_t *equeue,
+				  gxio_mpipe_context_t *context,
+				  unsigned int ering,
+				  unsigned int channel,
+				  void *mem, unsigned int mem_size,
+				  unsigned int mem_flags);
+
+/* Reserve completion slots for edescs.
+ *
+ * Use gxio_mpipe_equeue_put_at() to actually populate the slots.
+ *
+ * This function is slower than gxio_mpipe_equeue_reserve_fast(), but
+ * returns a full 64 bit completion slot, which can be used with
+ * gxio_mpipe_equeue_is_complete().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param num Number of slots to reserve (must be non-zero).
+ * @return The first reserved completion slot, or a negative error code.
+ */
+static inline int64_t gxio_mpipe_equeue_reserve(gxio_mpipe_equeue_t *equeue,
+						unsigned int num)
+{
+	return __gxio_dma_queue_reserve_aux(&equeue->dma_queue, num, true);
+}
+
+/* Reserve completion slots for edescs, if possible.
+ *
+ * Use gxio_mpipe_equeue_put_at() to actually populate the slots.
+ *
+ * This function is slower than gxio_mpipe_equeue_try_reserve_fast(),
+ * but returns a full 64 bit completion slot, which can be used with
+ * gxio_mpipe_equeue_is_complete().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param num Number of slots to reserve (must be non-zero).
+ * @return The first reserved completion slot, or a negative error code.
+ */
+static inline int64_t gxio_mpipe_equeue_try_reserve(gxio_mpipe_equeue_t
+						    *equeue, unsigned int num)
+{
+	return __gxio_dma_queue_reserve_aux(&equeue->dma_queue, num, false);
+}
+
+/* Reserve slots for edescs.
+ *
+ * Use gxio_mpipe_equeue_put_at() to actually populate the slots.
+ *
+ * This function is faster than gxio_mpipe_equeue_reserve(), but
+ * returns a 24 bit slot (instead of a 64 bit completion slot), which
+ * thus cannot be used with gxio_mpipe_equeue_is_complete().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param num Number of slots to reserve (should be non-zero).
+ * @return The first reserved slot, or a negative error code.
+ */
+static inline int64_t gxio_mpipe_equeue_reserve_fast(gxio_mpipe_equeue_t
+						     *equeue, unsigned int num)
+{
+	return __gxio_dma_queue_reserve(&equeue->dma_queue, num, true, false);
+}
+
+/* Reserve slots for edescs, if possible.
+ *
+ * Use gxio_mpipe_equeue_put_at() to actually populate the slots.
+ *
+ * This function is faster than gxio_mpipe_equeue_try_reserve(), but
+ * returns a 24 bit slot (instead of a 64 bit completion slot), which
+ * thus cannot be used with gxio_mpipe_equeue_is_complete().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param num Number of slots to reserve (should be non-zero).
+ * @return The first reserved slot, or a negative error code.
+ */
+static inline int64_t gxio_mpipe_equeue_try_reserve_fast(gxio_mpipe_equeue_t
+							 *equeue,
+							 unsigned int num)
+{
+	return __gxio_dma_queue_reserve(&equeue->dma_queue, num, false, false);
+}
+
+/*
+ * HACK: This helper function tricks gcc 4.6 into avoiding saving
+ * a copy of "edesc->words[0]" on the stack for no obvious reason.
+ */
+
+static inline void gxio_mpipe_equeue_put_at_aux(gxio_mpipe_equeue_t *equeue,
+						uint_reg_t ew[2],
+						unsigned long slot)
+{
+	unsigned long edma_slot = slot & equeue->mask_num_entries;
+	gxio_mpipe_edesc_t *edesc_p = &equeue->edescs[edma_slot];
+
+	/*
+	 * ISSUE: Could set eDMA ring to be on generation 1 at start, which
+	 * would avoid the negation here, perhaps allowing "__insn_bfins()".
+	 */
+	ew[0] |= !((slot >> equeue->log2_num_entries) & 1);
+
+	/*
+	 * NOTE: We use "__gxio_mpipe_write()", plus the fact that the eDMA
+	 * queue alignment restrictions ensure that these two words are on
+	 * the same cacheline, to force proper ordering between the stores.
+	 */
+	__gxio_mmio_write64(&edesc_p->words[1], ew[1]);
+	__gxio_mmio_write64(&edesc_p->words[0], ew[0]);
+}
+
+/* Post an edesc to a given slot in an equeue.
+ *
+ * This function copies the supplied edesc into entry "slot mod N" in
+ * the underlying ring, setting the "gen" bit to the appropriate value
+ * based on "(slot mod N*2)", where "N" is the size of the ring.  Note
+ * that the higher bits of slot are unused, and thus, this function
+ * can handle "slots" as well as "completion slots".
+ *
+ * Normally this function is used to fill in slots reserved by
+ * gxio_mpipe_equeue_try_reserve(), gxio_mpipe_equeue_reserve(),
+ * gxio_mpipe_equeue_try_reserve_fast(), or
+ * gxio_mpipe_equeue_reserve_fast(),
+ *
+ * This function can also be used without "reserving" slots, if the
+ * application KNOWS that the ring can never overflow, for example, by
+ * pushing fewer buffers into the buffer stacks than there are total
+ * slots in the equeue, but this is NOT recommended.
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param edesc The egress descriptor to be posted.
+ * @param slot An egress slot (only the low bits are actually used).
+ */
+static inline void gxio_mpipe_equeue_put_at(gxio_mpipe_equeue_t *equeue,
+					    gxio_mpipe_edesc_t edesc,
+					    unsigned long slot)
+{
+	gxio_mpipe_equeue_put_at_aux(equeue, edesc.words, slot);
+}
+
+/* Post an edesc to the next slot in an equeue.
+ *
+ * This is a convenience wrapper around
+ * gxio_mpipe_equeue_reserve_fast() and gxio_mpipe_equeue_put_at().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param edesc The egress descriptor to be posted.
+ * @return 0 on success.
+ */
+static inline int gxio_mpipe_equeue_put(gxio_mpipe_equeue_t *equeue,
+					gxio_mpipe_edesc_t edesc)
+{
+	int64_t slot = gxio_mpipe_equeue_reserve_fast(equeue, 1);
+	if (slot < 0)
+		return (int)slot;
+
+	gxio_mpipe_equeue_put_at(equeue, edesc, slot);
+
+	return 0;
+}
+
+/* Ask the mPIPE hardware to egress outstanding packets immediately.
+ *
+ * This call is not necessary, but may slightly reduce overall latency.
+ *
+ * Technically, you should flush all gxio_mpipe_equeue_put_at() writes
+ * to memory before calling this function, to ensure the descriptors
+ * are visible in memory before the mPIPE hardware actually looks for
+ * them.  But this should be very rare, and the only side effect would
+ * be increased latency, so it is up to the caller to decide whether
+ * or not to flush memory.
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ */
+static inline void gxio_mpipe_equeue_flush(gxio_mpipe_equeue_t *equeue)
+{
+	/* Use "ring_idx = 0" and "count = 0" to "wake up" the eDMA ring. */
+	MPIPE_EDMA_POST_REGION_VAL_t val = { {0} };
+	/* Flush the write buffers. */
+	__insn_flushwb();
+	__gxio_mmio_write(equeue->dma_queue.post_region_addr, val.word);
+}
+
+/* Determine if a given edesc has been completed.
+ *
+ * Note that this function requires a "completion slot", and thus may
+ * NOT be used with a "slot" from gxio_mpipe_equeue_reserve_fast() or
+ * gxio_mpipe_equeue_try_reserve_fast().
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param completion_slot The completion slot used by the edesc.
+ * @param update If true, and the desc does not appear to have completed
+ * yet, then update any software cache of the hardware completion counter,
+ * and check again.  This should normally be true.
+ * @return True iff the given edesc has been completed.
+ */
+static inline int gxio_mpipe_equeue_is_complete(gxio_mpipe_equeue_t *equeue,
+						int64_t completion_slot,
+						int update)
+{
+	return __gxio_dma_queue_is_complete(&equeue->dma_queue,
+					    completion_slot, update);
+}
+
+/* Set the snf (store and forward) size for an equeue.
+ *
+ * The snf size for an equeue defaults to 1536, and encodes the size
+ * of the largest packet for which egress is guaranteed to avoid
+ * transmission underruns and/or corrupt checksums under heavy load.
+ *
+ * The snf size affects a global resource pool which cannot support,
+ * for example, all 24 equeues each requesting an snf size of 8K.
+ *
+ * To ensure that jumbo packets can be egressed properly, the snf size
+ * should be set to the size of the largest possible packet, which
+ * will usually be limited by the size of the app's largest buffer.
+ *
+ * This is a convenience wrapper around
+ * gxio_mpipe_config_edma_ring_blks().
+ *
+ * This function should not be called after any egress has been done
+ * on the equeue.
+ *
+ * @param equeue An egress queue initialized via gxio_mpipe_equeue_init().
+ * @param size The snf size, in bytes.
+ * @return Zero on success, negative error otherwise.
+ */
+static inline int gxio_mpipe_equeue_set_snf_size(gxio_mpipe_equeue_t *equeue,
+						 size_t size)
+{
+	int blks = (size + 127) / 128;
+	return gxio_mpipe_config_edma_ring_blks(equeue->context, equeue->ering,
+						blks + 1, blks, 1);
+}
+
+/*****************************************************************
+ *                        Link Management                         *
+ ******************************************************************/
+
+/*
+ *
+ * Functions for manipulating and sensing the state and configuration
+ * of physical network links.
+ *
+ * @section gxio_mpipe_link_perm Link Permissions
+ *
+ * Opening a link (with gxio_mpipe_link_open()) requests a set of link
+ * permissions, which control what may be done with the link, and potentially
+ * what permissions may be granted to other processes.
+ *
+ * Data permission allows the process to receive packets from the link by
+ * specifying the link's channel number in mPIPE packet distribution rules,
+ * and to send packets to the link by using the link's channel number as
+ * the target for an eDMA ring.
+ *
+ * Stats permission allows the process to retrieve link attributes (such as
+ * the speeds it is capable of running at, or whether it is currently up), and
+ * to read and write certain statistics-related registers in the link's MAC.
+ *
+ * Control permission allows the process to retrieve and modify link attributes
+ * (so that it may, for example, bring the link up and take it down), and
+ * read and write many registers in the link's MAC and PHY.
+ *
+ * Any permission may be requested as shared, which allows other processes
+ * to also request shared permission, or exclusive, which prevents other
+ * processes from requesting it.  In keeping with GXIO's typical usage in
+ * an embedded environment, the defaults for all permissions are shared.
+ *
+ * Permissions are granted on a first-come, first-served basis, so if two
+ * applications request an exclusive permission on the same link, the one
+ * to run first will win.  Note, however, that some system components, like
+ * the kernel Ethernet driver, may get an opportunity to open links before
+ * any applications run.
+ *
+ * @section gxio_mpipe_link_names Link Names
+ *
+ * Link names are of the form gbe<em>number</em> (for Gigabit Ethernet),
+ * xgbe<em>number</em> (for 10 Gigabit Ethernet), loop<em>number</em> (for
+ * internal mPIPE loopback), or ilk<em>number</em>/<em>channel</em>
+ * (for Interlaken links); for instance, gbe0, xgbe1, loop3, and
+ * ilk0/12 are all possible link names.  The correspondence between
+ * the link name and an mPIPE instance number or mPIPE channel number is
+ * system-dependent; all links will not exist on all systems, and the set
+ * of numbers used for a particular link type may not start at zero and may
+ * not be contiguous.  Use gxio_mpipe_link_enumerate() to retrieve the set of
+ * links which exist on a system, and always use gxio_mpipe_link_instance()
+ * to determine which mPIPE controls a particular link.
+ *
+ * Note that in some cases, links may share hardware, such as PHYs, or
+ * internal mPIPE buffers; in these cases, only one of the links may be
+ * opened at a time.  This is especially common with xgbe and gbe ports,
+ * since each xgbe port uses 4 SERDES lanes, each of which may also be
+ * configured as one gbe port.
+ *
+ * @section gxio_mpipe_link_states Link States
+ *
+ * The mPIPE link management model revolves around three different states,
+ * which are maintained for each link:
+ *
+ * 1. The <em>current</em> link state: is the link up now, and if so, at
+ *    what speed?
+ *
+ * 2. The <em>desired</em> link state: what do we want the link state to be?
+ *    The system is always working to make this state the current state;
+ *    thus, if the desired state is up, and the link is down, we'll be
+ *    constantly trying to bring it up, automatically.
+ *
+ * 3. The <em>possible</em> link state: what speeds are valid for this
+ *    particular link?  Or, in other words, what are the capabilities of
+ *    the link hardware?
+ *
+ * These link states are not, strictly speaking, related to application
+ * state; they may be manipulated at any time, whether or not the link
+ * is currently being used for data transfer.  However, for convenience,
+ * gxio_mpipe_link_open() and gxio_mpipe_link_close() (or application exit)
+ * can affect the link state.  These implicit link management operations
+ * may be modified or disabled by the use of link open flags.
+ *
+ * From an application, you can use gxio_mpipe_link_get_attr()
+ * and gxio_mpipe_link_set_attr() to manipulate the link states.
+ * gxio_mpipe_link_get_attr() with ::GXIO_MPIPE_LINK_POSSIBLE_STATE
+ * gets you the possible link state.  gxio_mpipe_link_get_attr() with
+ * ::GXIO_MPIPE_LINK_CURRENT_STATE gets you the current link state.
+ * Finally, gxio_mpipe_link_set_attr() and gxio_mpipe_link_get_attr()
+ * with ::GXIO_MPIPE_LINK_DESIRED_STATE allow you to modify or retrieve
+ * the desired link state.
+ *
+ * If you want to manage a link from a part of your application which isn't
+ * involved in packet processing, you can use the ::GXIO_MPIPE_LINK_NO_DATA
+ * flags on a gxio_mpipe_link_open() call.  This opens the link, but does
+ * not request data permission, so it does not conflict with any exclusive
+ * permissions which may be held by other processes.  You can then can use
+ * gxio_mpipe_link_get_attr() and gxio_mpipe_link_set_attr() on this link
+ * object to bring up or take down the link.
+ *
+ * Some links support link state bits which support various loopback
+ * modes. ::GXIO_MPIPE_LINK_LOOP_MAC tests datapaths within the Tile
+ * Processor itself; ::GXIO_MPIPE_LINK_LOOP_PHY tests the datapath between
+ * the Tile Processor and the external physical layer interface chip; and
+ * ::GXIO_MPIPE_LINK_LOOP_EXT tests the entire network datapath with the
+ * aid of an external loopback connector.  In addition to enabling hardware
+ * testing, such configuration can be useful for software testing, as well.
+ *
+ * When LOOP_MAC or LOOP_PHY is enabled, packets transmitted on a channel
+ * will be received by that channel, instead of being emitted on the
+ * physical link, and packets received on the physical link will be ignored.
+ * Other than that, all standard GXIO operations work as you might expect.
+ * Note that loopback operation requires that the link be brought up using
+ * one or more of the GXIO_MPIPE_LINK_SPEED_xxx link state bits.
+ *
+ * Those familiar with previous versions of the MDE on TILEPro hardware
+ * will notice significant similarities between the NetIO link management
+ * model and the mPIPE link management model.  However, the NetIO model
+ * was developed in stages, and some of its features -- for instance,
+ * the default setting of certain flags -- were shaped by the need to be
+ * compatible with previous versions of NetIO.  Since the features provided
+ * by the mPIPE hardware and the mPIPE GXIO library are significantly
+ * different than those provided by NetIO, in some cases, we have made
+ * different choices in the mPIPE link management API.  Thus, please read
+ * this documentation carefully before assuming that mPIPE link management
+ * operations are exactly equivalent to their NetIO counterparts.
+ */
+
+/* An object used to manage mPIPE link state and resources. */
+typedef struct {
+	/* The overall mPIPE context. */
+	gxio_mpipe_context_t *context;
+
+	/* The channel number used by this link. */
+	uint8_t channel;
+
+	/* The MAC index used by this link. */
+	uint8_t mac;
+} gxio_mpipe_link_t;
+
+/* Translate a link name to the instance number of the mPIPE shim which is
+ *  connected to that link.  This call does not verify whether the link is
+ *  currently available, and does not reserve any link resources;
+ *  gxio_mpipe_link_open() must be called to perform those functions.
+ *
+ *  Typically applications will call this function to translate a link name
+ *  to an mPIPE instance number; call gxio_mpipe_init(), passing it that
+ *  instance number, to initialize the mPIPE shim; and then call
+ *  gxio_mpipe_link_open(), passing it the same link name plus the mPIPE
+ *  context, to configure the link.
+ *
+ * @param link_name Name of the link; see @ref gxio_mpipe_link_names.
+ * @return The mPIPE instance number which is associated with the named
+ *  link, or a negative error code (::GXIO_ERR_NO_DEVICE) if the link does
+ *  not exist.
+ */
+extern int gxio_mpipe_link_instance(const char *link_name);
+
+/* Retrieve one of this system's legal link names, and its MAC address.
+ *
+ * @param index Link name index.  If a system supports N legal link names,
+ *  then indices between 0 and N - 1, inclusive, each correspond to one of
+ *  those names.  Thus, to retrieve all of a system's legal link names,
+ *  call this function in a loop, starting with an index of zero, and
+ *  incrementing it once per iteration until -1 is returned.
+ * @param link_name Pointer to the buffer which will receive the retrieved
+ *  link name.  The buffer should contain space for at least
+ *  ::GXIO_MPIPE_LINK_NAME_LEN bytes; the returned name, including the
+ *  terminating null byte, will be no longer than that.
+ * @param link_name Pointer to the buffer which will receive the retrieved
+ *  MAC address.  The buffer should contain space for at least 6 bytes.
+ * @return Zero if a link name was successfully retrieved; -1 if one was
+ *  not.
+ */
+extern int gxio_mpipe_link_enumerate_mac(int index, char *link_name,
+					 uint8_t *mac_addr);
+
+/* Open an mPIPE link.
+ *
+ *  A link must be opened before it may be used to send or receive packets,
+ *  and before its state may be examined or changed.  Depending up on the
+ *  link's intended use, one or more link permissions may be requested via
+ *  the flags parameter; see @ref gxio_mpipe_link_perm.  In addition, flags
+ *  may request that the link's state be modified at open time.  See @ref
+ *  gxio_mpipe_link_states and @ref gxio_mpipe_link_open_flags for more detail.
+ *
+ * @param link A link state object, which will be initialized if this
+ *  function completes successfully.
+ * @param context An initialized mPIPE context.
+ * @param link_name Name of the link.
+ * @param flags Zero or more @ref gxio_mpipe_link_open_flags, ORed together.
+ * @return 0 if the link was successfully opened, or a negative error code.
+ *
+ */
+extern int gxio_mpipe_link_open(gxio_mpipe_link_t *link,
+				gxio_mpipe_context_t *context,
+				const char *link_name, unsigned int flags);
+
+/* Close an mPIPE link.
+ *
+ *  Closing a link makes it available for use by other processes.  Once
+ *  a link has been closed, packets may no longer be sent on or received
+ *  from the link, and its state may not be examined or changed.
+ *
+ * @param link A link state object, which will no longer be initialized
+ *  if this function completes successfully.
+ * @return 0 if the link was successfully closed, or a negative error code.
+ *
+ */
+extern int gxio_mpipe_link_close(gxio_mpipe_link_t *link);
+
+/* Return a link's channel number.
+ *
+ * @param link A properly initialized link state object.
+ * @return The channel number for the link.
+ */
+static inline int gxio_mpipe_link_channel(gxio_mpipe_link_t *link)
+{
+	return link->channel;
+}
+
+/* Set a link attribute.
+ *
+ * @param link A properly initialized link state object.
+ * @param attr An attribute from the set of @ref gxio_mpipe_link_attrs.
+ * @param val New value of the attribute.
+ * @return 0 if the attribute was successfully set, or a negative error
+ *  code.
+ */
+extern int gxio_mpipe_link_set_attr(gxio_mpipe_link_t *link, uint32_t attr,
+				    int64_t val);
+
+///////////////////////////////////////////////////////////////////
+//                             Timestamp                         //
+///////////////////////////////////////////////////////////////////
+
+/* Get the timestamp of mPIPE when this routine is called.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ts A timespec structure to store the current clock.
+ * @return If the call was successful, zero; otherwise, a negative error
+ *  code.
+ */
+extern int gxio_mpipe_get_timestamp(gxio_mpipe_context_t *context,
+				    struct timespec64 *ts);
+
+/* Set the timestamp of mPIPE.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ts A timespec structure to store the requested clock.
+ * @return If the call was successful, zero; otherwise, a negative error
+ *  code.
+ */
+extern int gxio_mpipe_set_timestamp(gxio_mpipe_context_t *context,
+				    const struct timespec64 *ts);
+
+/* Adjust the timestamp of mPIPE.
+ *
+ * @param context An initialized mPIPE context.
+ * @param delta A signed time offset to adjust, in nanoseconds.
+ * The absolute value of this parameter must be less than or
+ * equal to 1000000000.
+ * @return If the call was successful, zero; otherwise, a negative error
+ *  code.
+ */
+extern int gxio_mpipe_adjust_timestamp(gxio_mpipe_context_t *context,
+				       int64_t delta);
+
+/** Adjust the mPIPE timestamp clock frequency.
+ *
+ * @param context An initialized mPIPE context.
+ * @param ppb A 32-bit signed PPB (Parts Per Billion) value to adjust.
+ * The absolute value of ppb must be less than or equal to 1000000000.
+ * Values less than about 30000 will generally cause a GXIO_ERR_INVAL
+ * return due to the granularity of the hardware that converts reference
+ * clock cycles into seconds and nanoseconds.
+ * @return If the call was successful, zero; otherwise, a negative error
+ *  code.
+ */
+extern int gxio_mpipe_adjust_timestamp_freq(gxio_mpipe_context_t* context,
+                                            int32_t ppb);
+
+#endif /* !_GXIO_MPIPE_H_ */