On 7/18/2025 12:36 PM, Bjorn Helgaas wrote:
On Fri, Jul 18, 2025 at 12:29:05PM -0500, Mario Limonciello wrote:
On 7/18/2025 12:25 PM, Bjorn Helgaas wrote:
On Thu, Jul 17, 2025 at 12:38:12PM -0500, Mario Limonciello wrote:
From: Mario Limonciello <mario.limoncie...@amd.com>
On systems with multiple GPUs there can be uncertainty which GPU is the
primary one used to drive the display at bootup. In some desktop
environments this can lead to increased power consumption because
secondary GPUs may be used for rendering and never go to a low power
state. In order to disambiguate this add a new sysfs attribute
'boot_display' that uses the output of video_is_primary_device() to
populate whether a PCI device was used for driving the display.
+What: /sys/bus/pci/devices/.../boot_display
+Date: October 2025
+Contact: Linux PCI developers <linux-...@vger.kernel.org>
+Description:
+ This file indicates that displays connected to the device were
+ used to display the boot sequence. If a display connected to
+ the device was used to display the boot sequence the file will
+ be present and contain "1".
int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
{
+ int retval;
+
if (!sysfs_initialized)
return -EACCES;
+ retval = pci_create_boot_display_file(pdev);
In addition to Mani's question about whether /sys/bus/pci/ is the
right place for this (which is a very good question), it's also been
pointed out to me that we've been trying to get rid of
pci_create_sysfs_dev_files() for years.
If it's possible to make this a static attribute that would be much,
much cleaner.
Right - I tried to do this, but the problem is at the time the PCI device is
created the information needed to make the judgement isn't ready. The
options end up being:
* a sysfs file for every display device with 0/1
* a sysfs file that is not accurate until later in the boot
What's missing? The specifics might be helpful if someone has another
crack at getting rid of pci_create_sysfs_dev_files() in the future.
The underlying SCREEN_INFO code tries to walk through all the PCI
devices in a loop, but at the time all the devices are walked the memory
regions associated with the device weren't populated.
So my earlier hack was to re-run the screen info check, and it was awful.
So IMO it /needs/ to come later.
+ if (retval)
+ return retval;
+
return pci_create_resource_files(pdev);
}
@@ -1671,6 +1716,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
if (!sysfs_initialized)
return;
+ pci_remove_boot_display_file(pdev);
pci_remove_resource_files(pdev);
}
--
2.43.0
