[PATCH v8 9/9] PCI: Add a new 'boot_display' attribute

[Maxime Ripard]

Hi Mario,

On Mon, Jul 14, 2025 at 04:21:46PM -0500, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello at 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 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.
> 
> Reviewed-by: Thomas Zimmermann <tzimmermann at suse.de>
> Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
> ---
> v7:
>  * fix lkp failure
>  * Add tag
> v6:
>  * Only show for the device that is boot display
>  * Only create after PCI device sysfs files are initialized to ensure
>    that resources are ready.
> v4:
>  * new patch
> ---
>  Documentation/ABI/testing/sysfs-bus-pci |  8 +++++
>  drivers/pci/pci-sysfs.c                 | 46 +++++++++++++++++++++++++
>  2 files changed, 54 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index 69f952fffec72..8b455b1a58852 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -612,3 +612,11 @@ Description:
>  
>  		  # ls doe_features
>  		  0001:01        0001:02        doe_discovery
> +
> +What:		/sys/bus/pci/devices/.../boot_display
> +Date:		October 2025
> +Contact:	Linux PCI developers <linux-pci at vger.kernel.org>
> +Description:
> +		This file indicates the device was used as a boot
> +		display. If the device was used as the boot display, the file
> +		will be present and contain "1".

It would probably be a good idea to define what a "boot display" here
is. I get what you mean, but it's pretty vague and could easily be
misunderstood.

Maxime
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