From: Emil Velikov <emil.veli...@collabora.com> Currently the revision isn't available via sysfs/libudev thus if one wants to know the value they need to read through the config file.
This in itself wakes/powers up the device, causing unwanted delay since it can be quite costly. There are at least two userspace components which could make use the new file libpciaccess and libdrm. The former [used in various places] wakes up _every_ PCI device, which can be observed via glxinfo [when using Mesa 10.0+ drivers]. While the latter [in association with Mesa 13.0] can lead to 2-3 second delays while starting firefox, thunderbird or chromium. Expose the revision as a separate file, just like we do for the device, vendor, their subsystem version and class. Cc: Bjorn Helgaas <bhelgaas at google.com> Cc: linux-pci at vger.kernel.org Cc: Greg KH <gregkh at linuxfoundation.org> Link: https://bugs.freedesktop.org/show_bug.cgi?id=98502 Tested-by: Mauro Santos <registo.mailling at gmail.com> Reviewed-by: Alex Deucher <alexander.deucher at amd.com> Signed-off-by: Emil Velikov <emil.velikov at collabora.com> --- v2: Add r-b/t-b tags, slim down CC list, add note about userspace. v3: Add Documentation/ bits (Greg KH) Gents, please keep me in the CC list. Thanks Emil --- Documentation/ABI/testing/sysfs-bus-pci | 7 +++++++ Documentation/filesystems/sysfs-pci.txt | 2 ++ drivers/pci/pci-sysfs.c | 2 ++ 3 files changed, 11 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index b3bc50f..5a1732b 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -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 at 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. diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt index 74eaac2..6ea1ced 100644 --- a/Documentation/filesystems/sysfs-pci.txt +++ b/Documentation/filesystems/sysfs-pci.txt @@ -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) diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index bcd10c7..0666287 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -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, -- 2.9.3
