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PCI: Allow read/write access to sysfs I/O port resources

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PCI sysfs resource files currently only allow mmap'ing.  On x86 this
works fine for memory backed BARs, but doesn't work at all for I/O
port backed BARs.  Add read/write to I/O port PCI sysfs resource
files to allow userspace access to these device regions.

Acked-by: Chris Wright <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>
Signed-off-by: Jesse Barnes <[email protected]>
This commit is contained in:
Alex Williamson 2010-07-19 09:45:34 -06:00 • committed by Jesse Barnes
commit 8633328be2
2 changed files with 73 additions and 2 deletions
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7
Documentation/filesystems/sysfs-pci.txt
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@ -39,7 +39,7 @@ files, each with their own function.
local_cpus nearby CPU mask (cpumask, ro)
remove remove device from kernel's list (ascii, wo)
resource PCI resource host addresses (ascii, ro)
resource0..N PCI resource N, if present (binary, mmap)
resource0..N PCI resource N, if present (binary, mmap, rw[1])
resource0_wc..N_wc PCI WC map resource N, if prefetchable (binary, mmap)
rom PCI ROM resource, if present (binary, ro)
subsystem_device PCI subsystem device (ascii, ro)
@ -54,13 +54,16 @@ files, each with their own function.
binary - file contains binary data
cpumask - file contains a cpumask type
[1] rw for RESOURCE_IO (I/O port) regions only
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.
value from any attempted mmap. The most notable of these are I/O port
resources, which also provide read/write access.
The 'enable' file provides a counter that indicates how many times the device
has been enabled. If the 'enable' file currently returns '4', and a '1' is