Re: [PATCH 04/11] video/aperture: use generic code to figure out the vga default device

From: Thomas Zimmermann
Date: Wed Jan 11 2023 - 10:59:37 EST

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.

I've long wanted to rework this helper anyway. So this is a good opportunity.

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

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