[PATCH v8 0/9] Adjust fbcon console device detection

[Bjorn Helgaas]

On Mon, Jul 14, 2025 at 04:21:37PM -0500, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello at amd.com>
> 
> This series started out as changes to VGA arbiter to try to handle a case
> of a system with 2 GPUs that are not VGA devices.  This was discussed
> but decided not to overload the VGA arbiter for non VGA devices.
> 
> Instead move the x86 specific detection of framebuffer resources into x86
> specific code that the fbcon can use to properly identify the primary
> device. This code is still called from the VGA arbiter, and the logic does
> not change there. To avoid regression default to VGA arbiter and only fall
> back to looking up with x86 specific detection method.
> 
> In order for userspace to also be able to discover which device was the
> primary video display device create a new sysfs file 'boot_display'.
> 
> A matching userspace implementation for this file is available here:
> Link: https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/merge_requests/39
> Link: https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2038
> 
> Dave Airlie has been pinged for a comment on this approach.
> Dave had suggested in the past [1]:
> 
> "
>  But yes if that doesn't work, then maybe we need to make the boot_vga
>  flag mean boot_display_gpu, and fix it in the kernel
> "
> 
> This was one of the approached tried in earlier revisions and it was
> rejected in favor of creating a new sysfs file (which is what this
> version does).
> 
> It is suggested that this series merge entirely through the PCI tree.
> 
> Link: https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/merge_requests/37#note_2938602 [1]

There's an underlying bug that we're trying to fix with this series
and the related libpciaccess and xserver changes, isn't there?  Can we
include that somewhere to help motivate this?  (I guess it's really
only the last two or three patches that are strictly related, right?)

> v8 fixes an LKP robot reported issue
> 
> Mario Limonciello (9):
>   PCI: Add helper for checking if a PCI device is a display controller
>   vfio/pci: Use pci_is_display()
>   vga_switcheroo: Use pci_is_display()
>   iommu/vt-d: Use pci_is_display()
>   ALSA: hda: Use pci_is_display()
>   Fix access to video_is_primary_device() when compiled without
>     CONFIG_VIDEO
>   PCI/VGA: Replace vga_is_firmware_default() with a screen info check
>   fbcon: Use screen info to find primary device
>   PCI: Add a new 'boot_display' attribute
> 
>  Documentation/ABI/testing/sysfs-bus-pci |  8 +++++
>  arch/parisc/include/asm/video.h         |  2 +-
>  arch/sparc/include/asm/video.h          |  2 ++
>  arch/x86/include/asm/video.h            |  2 ++
>  arch/x86/video/video-common.c           | 17 ++++++++-
>  drivers/gpu/vga/vga_switcheroo.c        |  2 +-
>  drivers/iommu/intel/iommu.c             |  2 +-
>  drivers/pci/pci-sysfs.c                 | 46 +++++++++++++++++++++++++
>  drivers/pci/vgaarb.c                    | 31 +++--------------
>  drivers/vfio/pci/vfio_pci_igd.c         |  3 +-
>  include/linux/pci.h                     | 15 ++++++++
>  sound/hda/hdac_i915.c                   |  2 +-
>  sound/pci/hda/hda_intel.c               |  4 +--
>  13 files changed, 101 insertions(+), 35 deletions(-)
> 
> -- 
> 2.43.0
>