Hi
Am 16.06.25 um 08:50 schrieb David Airlie:
[...]
It's also a bit concerning that we're making a policy decision here
that the integrated graphics is the "boot VGA" device, among two
non-VGA devices. I think vgaarb has a similar legacy policy decision
for VGA devices that it's stuck with, but it's not clear to me that
reiterating the policy selection here is still correct. Thanks,
Alex
I'm with you there. That's actually exactly why the first swing at
this was with a patch to userspace.
https://gitlab.freedesktop.org/xorg/lib/libpciaccess/-/merge_requests/37
I second Alex' point. I acked the patch purely on my understanding of
how it does this, but as I noted, I'd also prefer to solve this in user
space. I think we should push back on this change.
If we are solving this in userspace I think fixing it in libpciaccess
is probably also the wrong place, which leaves open where is the right
place?
Why is libpciaccess the wrong place? I see that the boot display is not
necessarily on the PCI bus. But if its not handled in libpciaccess,
should it rather go into Xorg directly?
To be honest the what GPU is driving the display at boot hint should
come from the kernel, since it knows already, whether boot_vga is the
best method of doing that is open to questions.
The proposed user-space patch looks way less intrusive than the kernel
change.
It might be better to have a bit somewhere on the drm device that shows this.
hello new UAPI.
In the kernel, there's already video_is_primary_device. [1] On x86, it
looks at vga_default_device(), on other architectures, it looks at
firmware settings. If there's no default vga on x86, it could do more
heuristics to figure out the boot display. The result can be exported by
a boot_display file via sysfs. video_is_primary_device() is currently
used by fbcon. Any changes to the helper would likely benefit fbcon as well.
Best regards
Thomas
[1]
https://elixir.bootlin.com/linux/v6.15.2/source/include/asm-generic/video.h#L28
Dave.
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Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
