Commit 702ed3be authored by Emil Velikov's avatar Emil Velikov Committed by Bjorn Helgaas
Browse files

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: default avatarMauro Santos <registo.mailling@gmail.com>
Signed-off-by: default avatarEmil Velikov <emil.velikov@collabora.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
CC: Greg KH <gregkh@linuxfoundation.org>
parent 1001354c

Documentation/ABI/testing/sysfs-bus-pci

+7 −0
Original line number Diff line number Diff line
@@ -294,3 +294,10 @@ Description: 
		a firmware bug to the system vendor.  Writing to this file

		taints the kernel with TAINT_FIRMWARE_WORKAROUND, which

		reduces the supportability of your system.



What:		/sys/bus/pci/devices/.../revision

Date:		November 2016

Contact:	Emil Velikov <emil.l.velikov@gmail.com>

Description:

		This file contains the revision field of the the PCI device.

		The value comes from device config space. The file is read only.

Documentation/filesystems/sysfs-pci.txt

+2 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ that support it. For example, a given bus might look like this: 
     |   |-- resource0

     |   |-- resource1

     |   |-- resource2

     |   |-- revision

     |   |-- rom

     |   |-- subsystem_device

     |   |-- subsystem_vendor
@@ -41,6 +42,7 @@ files, each with their own function. 
       resource		   PCI resource host addresses (ascii, ro)

       resource0..N	   PCI resource N, if present (binary, mmap, rw[1])

       resource0_wc..N_wc  PCI WC map resource N, if prefetchable (binary, mmap)

       revision		   PCI revision (ascii, ro)

       rom		   PCI ROM resource, if present (binary, ro)

       subsystem_device	   PCI subsystem device (ascii, ro)

       subsystem_vendor	   PCI subsystem vendor (ascii, ro)

drivers/pci/pci-sysfs.c

+2 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ pci_config_attr(vendor, "0x%04x\n"); 
pci_config_attr(device, "0x%04x\n");

pci_config_attr(subsystem_vendor, "0x%04x\n");

pci_config_attr(subsystem_device, "0x%04x\n");

pci_config_attr(revision, "0x%02x\n");

pci_config_attr(class, "0x%06x\n");

pci_config_attr(irq, "%u\n");
@@ -568,6 +569,7 @@ static struct attribute *pci_dev_attrs[] = { 
	&dev_attr_device.attr,

	&dev_attr_subsystem_vendor.attr,

	&dev_attr_subsystem_device.attr,

	&dev_attr_revision.attr,

	&dev_attr_class.attr,

	&dev_attr_irq.attr,

	&dev_attr_local_cpus.attr,

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