linux-kernel - Re: [PATCH 10/12] fbdev/core: Use fb_is_primary_device() in fb_firmware

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Date:   Wed, 05 Jul 2023 10:02:27 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>, arnd@...db.de,
        deller@....de, daniel@...ll.ch, airlied@...il.com
Cc:     linux-hyperv@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mips@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-csky@...r.kernel.org, Antonino Daplas <adaplas@...il.com>,
        Maik Broemme <mbroemme@...mpq.org>, loongarch@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-alpha@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 10/12] fbdev/core: Use fb_is_primary_device() in
 fb_firmware_edid()

Thomas Zimmermann <tzimmermann@...e.de> writes:

> Detect the primary VGA device with fb_is_primary_device() in the
> implementation of fb_firmware_edid(). Remove the existing code.
>

An explanation about why this is possible would be useful here.

> Adapt the function to receive an instance of struct fb_info and
> update all callers.
>

[...]

> -const unsigned char *fb_firmware_edid(struct device *device)
> +const unsigned char *fb_firmware_edid(struct fb_info *info)
>  {
> -	struct pci_dev *dev = NULL;
> -	struct resource *res = NULL;
>  	unsigned char *edid = NULL;
>  
> -	if (device)
> -		dev = to_pci_dev(device);
> -
> -	if (dev)
> -		res = &dev->resource[PCI_ROM_RESOURCE];
> -
> -	if (res && res->flags & IORESOURCE_ROM_SHADOW)

This open codes what used to be the fb_is_primary_device() logic before
commit 5ca1479cd35d ("fbdev: Simplify fb_is_primary_device for x86").
But now after that commit there is functional change since the ROM
shadowing check would be dropped.

I believe that's OK and Sima explains in their commit message that
vga_default_device() should be enough and the check is redundant.

Still, I think that this change should be documented in your commit
message. 

With that change,

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat