On Wed, Jan 11, 2023 at 04:59:30PM +0100, Thomas Zimmermann wrote:
> Hi
>
> Am 11.01.23 um 16:41 schrieb Daniel Vetter:
> > Since vgaarb has been promoted to be a core piece of the pci subsystem
> > we don't have to open code random guesses anymore, we actually know
> > this in a platform agnostic way, and there's no need for an x86
> > specific hack. See also 1d38fe6ee6a8 ("PCI/VGA: Move vgaarb to
> > drivers/pci")
> >
> > This should not result in any functional change, and the non-x86
> > multi-gpu pci systems are probably rare enough to not matter (I don't
> > know of any tbh). But it's a nice cleanup, so let's do it.
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> > Cc: Helge Deller <deller@xxxxxx>
> > Cc: linux-fbdev@xxxxxxxxxxxxxxx
> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Cc: linux-pci@xxxxxxxxxxxxxxx
> > ---
> > drivers/video/aperture.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
> > index 41e77de1ea82..3d8c925c7365 100644
> > --- a/drivers/video/aperture.c
> > +++ b/drivers/video/aperture.c
> > @@ -324,13 +324,11 @@ EXPORT_SYMBOL(aperture_remove_conflicting_devices);
> > */
> > int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name)
> > {
> > - bool primary = false;
> > + bool primary;
> > resource_size_t base, size;
> > int bar, ret;
> > -#ifdef CONFIG_X86
> > - primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
> > -#endif
> > + primary = pdev == vga_default_device();
>
> vga_default_device() is part of vgaarb and can return NULL. [1] That new
> test is likely to be incorrect on many systems.
>
> I suggest to implement a helper like fb_is_primary_device() on x86: it uses
> the default VGA if set, or falls back to the original test. [2]
>
> It's noteworthy that on most architectures, fb_is_primary_device() returns
> 0. But at least on Sparc [3] and some Parisc [4] machines, it does not.
Afaik these neither do legacy vga nor sysfb, so we should be fine. I'll
augment the commit message.
> I've long wanted to rework this helper anyway. So this is a good
> opportunity.
Hm yeah that sounds like a good thing to copy. I'm honestly not sure
whether it's needed, but at least it shouldn't hurt. I thought at least
that the boot default device should be set on all pci architectures.
I'll also reorder this with the previous patch to avoid the compile fail.
-Daniel
>
> Best regards
> Thomas
>
> [1]
> https://elixir.bootlin.com/linux/latest/source/include/linux/vgaarb.h#L69
> [2]
> https://elixir.bootlin.com/linux/latest/source/arch/x86/video/fbdev.c#L14
> [3] https://elixir.bootlin.com/linux/latest/source/arch/sparc/include/asm/fb.h#L18
> [4] https://elixir.bootlin.com/linux/latest/source/drivers/video/console/sticore.c#L1153
>
>
> > for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
> > if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Ivo Totev
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
