linux-kernel - Re: [PATCH v10 3/4] fbcon: Use screen info to find primary device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250904204256.GA1277756@bhelgaas>
Date: Thu, 4 Sep 2025 15:42:56 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: "Mario Limonciello (AMD)" <superm1@...nel.org>
Cc: David Airlie <airlied@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	"open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
	Daniel Dadap <ddadap@...dia.com>
Subject: Re: [PATCH v10 3/4] fbcon: Use screen info to find primary device

On Mon, Aug 11, 2025 at 11:26:05AM -0500, Mario Limonciello (AMD) wrote:
> On systems with non VGA GPUs fbcon can't find the primary GPU because
> video_is_primary_device() only checks the VGA arbiter.
> 
> Add a screen info check to video_is_primary_device() so that callers
> can get accurate data on such systems.
> 
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
> Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>

Reviewed-by: Bjorn Helgaas <bhelgaas@...gle.com>

I don't think you need my ack for this, but it does look fine to me.

I wish __screen_info_pci_dev() didn't have to use pci_get_base_class()
to iterate through all the devices, but you didn't change that and
maybe somebody will dream up a more efficient way someday.

Let me know if you need anything more from me.  Thanks for persevering
with this!

> ---
> v10:
>  * Rebase on 6.17-rc1
>  * Squash 'fbcon: Stop using screen_info_pci_dev()'
> ---
>  arch/x86/video/video-common.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c
> index 81fc97a2a837a..e0aeee99bc99e 100644
> --- a/arch/x86/video/video-common.c
> +++ b/arch/x86/video/video-common.c
> @@ -9,6 +9,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/screen_info.h>
>  #include <linux/vgaarb.h>
>  
>  #include <asm/video.h>
> @@ -27,6 +28,11 @@ EXPORT_SYMBOL(pgprot_framebuffer);
>  
>  bool video_is_primary_device(struct device *dev)
>  {
> +#ifdef CONFIG_SCREEN_INFO
> +	struct screen_info *si = &screen_info;
> +	struct resource res[SCREEN_INFO_MAX_RESOURCES];
> +	ssize_t i, numres;
> +#endif
>  	struct pci_dev *pdev;
>  
>  	if (!dev_is_pci(dev))
> @@ -34,7 +40,24 @@ bool video_is_primary_device(struct device *dev)
>  
>  	pdev = to_pci_dev(dev);
>  
> -	return (pdev == vga_default_device());
> +	if (!pci_is_display(pdev))
> +		return false;
> +
> +	if (pdev == vga_default_device())
> +		return true;
> +
> +#ifdef CONFIG_SCREEN_INFO
> +	numres = screen_info_resources(si, res, ARRAY_SIZE(res));
> +	for (i = 0; i < numres; ++i) {
> +		if (!(res[i].flags & IORESOURCE_MEM))
> +			continue;
> +
> +		if (pci_find_resource(pdev, &res[i]))
> +			return true;
> +	}
> +#endif
> +
> +	return false;
>  }
>  EXPORT_SYMBOL(video_is_primary_device);
>  
> -- 
> 2.43.0
>