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diff --git a/docs/overview b/docs/overview deleted file mode 100644 index 87c1d1df10..0000000000 --- a/docs/overview +++ /dev/null @@ -1,102 +0,0 @@ -------------------------------------------------------------------------- - This is a proposal from the early days of udev. A lot of the things - mentioned here are implemented differently and most of the features - implemented in udev are not part of that document. - This document is only kept in the tree for sentimental reasons. -------------------------------------------------------------------------- - -We've got a couple of goals for udev: - -1) dynamic replacement for /dev -2) device naming -3) API to access info about current system devices - -Splitting these goals into separate subsystems: - -1) udev - dynamic replacement for /dev -2) namedev - device naming -3) libsysfs - a standard library for accessing device information on the - system. - -Udev ------- - -Udev will be responsible for responding to /sbin/hotplug on device -events. It will receive the device class information along with -device's sysfs directory. Udev will call the name_device function from -the naming device subsystem with that information and receive a unique -device name in return. Udev will then query sysfs through the libsysfs -for specific device information required for creating the /dev node like -major and minor number. Once it has the important information, udev -will create a /dev entry for the device, add the device to the in memory -table of current devices, and send notification of the successful event -through a D-BUS message. On a remove call, udev will remove the /dev -entry, remove the device from the in memory table, and send -notification. - -Udev will consist of a command udev - to be called from /sbin/hotplug. -It will require the in memory dynamic database/table for keeping track -of current system devices, and a library of routines for accessing that -database/table. Udev will not care about "how" devices are named, that -will be separated into the device naming subsystem. It's presented a -common device naming API by the device naming subsystem to use for -naming devices. - - - -namedev ----------- - -From comments people have made, the device naming part of udev has been -pushed into its own "subsystem". The reason is to make this as flexible -and pluggable as possible. The device naming subsystem, or namedev, will -present a standard interface for udev to call for naming a particular -device. Under that interface, system administrators can plug in their -own methods for device naming. - -We would provide a default naming scheme. The first prototype -implementation could simply take the sysfs directory passed in with the -device name function, query sysfs for the major and minor numbers, and -then look up in a static device name mapping file the name of the -device. The static device naming file could look just like devices.txt -in the Linux kernel's Documentation directory. Obviously, this isn't a -great implementation because eventually we'd like major an minor numbers -to be dynamic. - -The default naming scheme in the future would have a set of policies to -go through in order to determine the name of the device. The device -naming subsystem would get the sysfs directory of the to be named device -and would use the following information in order to map the device's -name: - -1) Label info - like SCSI's UUID -2) Bus Device Number -3) Topology on Bus -4) Kernel Name - DEFAULT - -System administrators could use the default naming system or enterprise -computing environments could plug in their Universal Unique Identifier -(UUID) policies. The idea is to make the device naming as flexible and -pluggable as possible. - -The device naming subsystem would require accessing sysfs for device -information. It will receive the device's sysfs directory in the call -from udev and use it to get more information to determine naming. The -namedev subsystem will include a standard naming API for udev to use. -The default naming scheme will include a set of functions and a static -device naming file, which will reside in /etc or /var. - - - -libsysfs --------- - -There is a need for a common API to access device information in sysfs. -The device naming subsystem and the udev subsystem need to take the -sysfs directory path and query device information. Instead of copying -code so each one will have to readdir, etc., splitting this logic of -sysfs calls into a separate library that will sit atop sysfs makes more -sense. Sysfs callbacks aren't standard across devices, so this is -another reason for creating a common and standard library interface for -querying device information. - |