PCI: Create revision file in sysfs
authorEmil Velikov <emil.velikov@collabora.com>
Mon, 21 Nov 2016 22:24:49 +0000 (16:24 -0600)
committerBjorn Helgaas <bhelgaas@google.com>
Mon, 21 Nov 2016 22:25:32 +0000 (16:25 -0600)
commit702ed3be1b1bf4dea05954168321741c0910c645
tree4148dde5865bb993433dbf80be09d7a26b2121ca
parent1001354ca34179f3db924eb66672442a173147dc
PCI: Create revision file in sysfs

Currently the revision isn't available via sysfs/libudev thus if one wants
to know the value one needs to read through the config file, which can be
quite time-consuming because it wakes/powers up the device.

There are at least two userspace components which could make use the new
file: libpciaccess and libdrm.  The former wakes up _every_ PCI device,
which can be observed via glxinfo when using Mesa 10.0+ drivers.  The
latter, in association with Mesa 13.0, can lead to 2-3 second delays while
starting firefox, thunderbird or chromium.

Link: https://bugs.freedesktop.org/show_bug.cgi?id=98502
Tested-by: Mauro Santos <registo.mailling@gmail.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch
CC: Greg KH <gregkh@linuxfoundation.org>
Documentation/ABI/testing/sysfs-bus-pci
Documentation/filesystems/sysfs-pci.txt
drivers/pci/pci-sysfs.c