summaryrefslogtreecommitdiff
path: root/Documentation/ABI/testing/sysfs-firmware-memmap
diff options
context:
space:
mode:
authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /Documentation/ABI/testing/sysfs-firmware-memmap
Initial import
Diffstat (limited to 'Documentation/ABI/testing/sysfs-firmware-memmap')
-rw-r--r--Documentation/ABI/testing/sysfs-firmware-memmap71
1 files changed, 71 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-firmware-memmap b/Documentation/ABI/testing/sysfs-firmware-memmap
new file mode 100644
index 000000000..eca0d6508
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-memmap
@@ -0,0 +1,71 @@
+What: /sys/firmware/memmap/
+Date: June 2008
+Contact: Bernhard Walle <bernhard.walle@gmx.de>
+Description:
+ On all platforms, the firmware provides a memory map which the
+ kernel reads. The resources from that memory map are registered
+ in the kernel resource tree and exposed to userspace via
+ /proc/iomem (together with other resources).
+
+ However, on most architectures that firmware-provided memory
+ map is modified afterwards by the kernel itself, either because
+ the kernel merges that memory map with other information or
+ just because the user overwrites that memory map via command
+ line.
+
+ kexec needs the raw firmware-provided memory map to setup the
+ parameter segment of the kernel that should be booted with
+ kexec. Also, the raw memory map is useful for debugging. For
+ that reason, /sys/firmware/memmap is an interface that provides
+ the raw memory map to userspace.
+
+ The structure is as follows: Under /sys/firmware/memmap there
+ are subdirectories with the number of the entry as their name:
+
+ /sys/firmware/memmap/0
+ /sys/firmware/memmap/1
+ /sys/firmware/memmap/2
+ /sys/firmware/memmap/3
+ ...
+
+ The maximum depends on the number of memory map entries provided
+ by the firmware. The order is just the order that the firmware
+ provides.
+
+ Each directory contains three files:
+
+ start : The start address (as hexadecimal number with the
+ '0x' prefix).
+ end : The end address, inclusive (regardless whether the
+ firmware provides inclusive or exclusive ranges).
+ type : Type of the entry as string. See below for a list of
+ valid types.
+
+ So, for example:
+
+ /sys/firmware/memmap/0/start
+ /sys/firmware/memmap/0/end
+ /sys/firmware/memmap/0/type
+ /sys/firmware/memmap/1/start
+ ...
+
+ Currently following types exist:
+
+ - System RAM
+ - ACPI Tables
+ - ACPI Non-volatile Storage
+ - reserved
+
+ Following shell snippet can be used to display that memory
+ map in a human-readable format:
+
+ -------------------- 8< ----------------------------------------
+ #!/bin/bash
+ cd /sys/firmware/memmap
+ for dir in * ; do
+ start=$(cat $dir/start)
+ end=$(cat $dir/end)
+ type=$(cat $dir/type)
+ printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
+ done
+ -------------------- >8 ----------------------------------------