linux-kernel - Re: [PATCH v2] drivers/firmware: fix SYSFB depends to prevent build failures

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Message-ID: <e3f0f7a0-2130-18be-48a4-af1918017eca@redhat.com>
Date:   Tue, 27 Jul 2021 13:32:29 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Peter Robinson <pbrobinson@...il.com>,
        Mark Brown <broonie@...nel.org>,
        kernel test robot <lkp@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Colin Ian King <colin.king@...onical.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        John Stultz <john.stultz@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v2] drivers/firmware: fix SYSFB depends to prevent build
 failures

On 7/27/21 1:17 PM, Geert Uytterhoeven wrote:

[snip]

>> Not enabling this, would mean that a platform device to match a driver
>> supporting the EFI GOP framebuffer (e.g: simple{drm,fb} or efifb) will
>> not be registered. Which will lead to not having an early framebuffer.
> 
> Do all (embedded) EFI systems have a frame buffer?
>

That's a good question. I don't know if all EFI firmwares are expected
to provide a GOP or not. But even the u-boot EFI stub provides one, if
video output is supported by u-boot on that system.
 
> Perhaps SYSFB should be selected by SYSFB_SIMPLEFB, FB_VESA,
> and FB_EFI?
> 

It's another option, yes. I just thought that the use of select was not
encouraged and using depends was less fragile / error prone.

>> The logic used to be in drivers/firmware/efi/efi-init.c, that's built
>> in if CONFIG_EFI is enabled. We just consolidated both X86 and EFI:
>>
>> https://cgit.freedesktop.org/drm/drm-misc/commit/?id=8633ef82f101
> 
> Thanks, I'm aware of that commit, as I was just about to reply to it,
> when I saw the patch is this thread ;-)
>

Ok :)
 
Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat