Re: [PATCH v3] PCI/VGA: Select SCREEN_INFO on X86

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Oct 13, 2025 at 05:08:26PM -0500, Mario Limonciello (AMD) wrote:
> commit 337bf13aa9dda ("PCI/VGA: Replace vga_is_firmware_default() with
> a screen info check") introduced an implicit dependency upon SCREEN_INFO
> by removing the open coded implementation.
> 
> If a user didn't have CONFIG_SCREEN_INFO set vga_is_firmware_default()
> would now return false.  SCREEN_INFO is only used on X86 so add add a
> conditional select for SCREEN_INFO to ensure that the VGA arbiter works
> as intended.
> 
> Reported-by: Eric Biggers <ebiggers@kernel.org>
> Closes: https://lore.kernel.org/linux-pci/20251012182302.GA3412@sol/
> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 337bf13aa9dda ("PCI/VGA: Replace vga_is_firmware_default() with a screen info check")
> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>

Applied to pci/for-linus for v6.18, thanks!

> ---
>  drivers/pci/Kconfig  | 1 +
>  drivers/pci/vgaarb.c | 6 ++----
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 7065a8e5f9b14..f94f5d384362e 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -306,6 +306,7 @@ config VGA_ARB
>  	bool "VGA Arbitration" if EXPERT
>  	default y
>  	depends on (PCI && !S390)
> +	select SCREEN_INFO if X86
>  	help
>  	  Some "legacy" VGA devices implemented on PCI typically have the same
>  	  hard-decoded addresses as they did on ISA. When multiple PCI devices
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index b58f94ee48916..436fa7f4c3873 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -556,10 +556,8 @@ EXPORT_SYMBOL(vga_put);
>  
>  static bool vga_is_firmware_default(struct pci_dev *pdev)
>  {
> -#ifdef CONFIG_SCREEN_INFO
> -	struct screen_info *si = &screen_info;
> -
> -	return pdev == screen_info_pci_dev(si);
> +#if defined CONFIG_X86
> +	return pdev == screen_info_pci_dev(&screen_info);
>  #else
>  	return false;
>  #endif
> -- 
> 2.43.0
>