Re: [PATCH v2] x86/video: Only fall back to vga_default_device() without screen info

[Aaron Ma]

Hi Mario,

Tested your v2 patch + Xorg MR !2242 on the hybrid system
(AMD 0x0380 + NVIDIA 0x030000, EFI framebuffer on AMD).

Result:

  AMD:    boot_display=1, boot_vga absent
  NVIDIA: boot_display absent, boot_vga=1

Xorg now picks AMD correctly. boot_display is fixed.

Tested-by: Aaron Ma <aaron.ma@xxxxxxxxxxxxx>

Aaron

On Tue, Jun 23, 2026 at 10:15 PM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
>
> Some multi GPU systems may have a VGA compatible device, but that might
> not be used for display.  If due to enumeration order this device is
> found before the one actually used for display then multiple devices
> may show the boot_display attribute, confusing userspace.
>
> When screen info is valid, use it exclusively to find the primary
> device so that only the device backing the framebuffer is reported.
> Only when no framebuffer has been set up does it make sense to fall
> back to the default VGA device.  This ensures at most one primary
> graphics device, preferably the one with the framebuffer.
>
> Suggested-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Fixes: ad90860bd10ee ("fbcon: Use screen info to find primary device")
> Reported-by: Aaron Ma <aaron.ma@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-pci/20260618081803.2790848-1-aaron.ma@xxxxxxxxxxxxx/#t
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> v1->v2:
>   * Fix subject
>   * Keep vga_default_device() as fallback instead of remove all
>     together
>  arch/x86/video/video-common.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c
> index 152789f00fcda..8ed82fff7638e 100644
> --- a/arch/x86/video/video-common.c
> +++ b/arch/x86/video/video-common.c
> @@ -43,21 +43,26 @@ bool video_is_primary_device(struct device *dev)
>         if (!pci_is_display(pdev))
>                 return false;
>
> -       if (pdev == vga_default_device())
> -               return true;
> -
>  #ifdef CONFIG_SCREEN_INFO
>         numres = screen_info_resources(si, res, ARRAY_SIZE(res));
> -       for (i = 0; i < numres; ++i) {
> -               if (!(res[i].flags & IORESOURCE_MEM))
> -                       continue;
> +       if (numres > 0) {
> +               for (i = 0; i < numres; ++i) {
> +                       if (!(res[i].flags & IORESOURCE_MEM))
> +                               continue;
> +
> +                       if (pci_find_resource(pdev, &res[i]))
> +                               return true;
> +               }
>
> -               if (pci_find_resource(pdev, &res[i]))
> -                       return true;
> +               return false;
>         }
>  #endif
>
> -       return false;
> +       /*
> +        * No framebuffer was set up by the firmware/bootloader, so fall back
> +        * to the default VGA device.
> +        */
> +       return pdev == vga_default_device();
>  }
>  EXPORT_SYMBOL(video_is_primary_device);
>
> --
> 2.43.0
>