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[PATCH] PCI: document sysfs rom file interface 

idr gently pointed out today that not only is the sysfs rom file
interface somewhat unintuitive (despite my efforts and initial
implementation), but it's also undocumented!  This patch to
Documentation/filesystems/sysfs-pci.txt corrects the latter problem; the
former is a userland ABI now though, so we're stuck with it for awhile
at least.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
wifi-calibration
Jesse Barnes 2005-12-09 11:55:03 -08:00 committed by Greg Kroah-Hartman
parent ac7dc65ac0
commit 5d135dff53
1 changed files with 15 additions and 6 deletions
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21
Documentation/filesystems/sysfs-pci.txt
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@ -1,4 +1,5 @@
Accessing PCI device resources through sysfs
--------------------------------------------
sysfs, usually mounted at /sys, provides access to PCI resources on platforms
that support it. For example, a given bus might look like this:
@ -47,14 +48,21 @@ files, each with their own function.
binary - file contains binary data
cpumask - file contains a cpumask type
The read only files are informational, writes to them will be ignored.
Writable files can be used to perform actions on the device (e.g. changing
config space, detaching a device). mmapable files are available via an
mmap of the file at offset 0 and can be used to do actual device programming
from userspace. Note that some platforms don't support mmapping of certain
resources, so be sure to check the return value from any attempted mmap.
The read only files are informational, writes to them will be ignored, with
the exception of the 'rom' file. Writable files can be used to perform
actions on the device (e.g. changing config space, detaching a device).
mmapable files are available via an mmap of the file at offset 0 and can be
used to do actual device programming from userspace. Note that some platforms
don't support mmapping of certain resources, so be sure to check the return
value from any attempted mmap.
The 'rom' file is special in that it provides read-only access to the device's
ROM file, if available. It's disabled by default, however, so applications
should write the string "1" to the file to enable it before attempting a read
call, and disable it following the access by writing "0" to the file.
Accessing legacy resources through sysfs
----------------------------------------
Legacy I/O port and ISA memory resources are also provided in sysfs if the
underlying platform supports them. They're located in the PCI class heirarchy,
@ -75,6 +83,7 @@ simply dereference the returned pointer (after checking for errors of course)
to access legacy memory space.
Supporting PCI access on new platforms
--------------------------------------
In order to support PCI resource mapping as described above, Linux platform
code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.