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

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Message-ID: <f9df82c9-1e1a-d657-d712-312f5f17cab0@redhat.com>
Date:   Tue, 27 Jul 2021 12:22:11 +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

Hello Geert,

On 7/27/21 12:03 PM, Geert Uytterhoeven wrote:

[snip]

> Thanks for your patch!
>

You are welcome.

>> --- a/drivers/firmware/Kconfig
>> +++ b/drivers/firmware/Kconfig
>> @@ -254,7 +254,7 @@ config QCOM_SCM_DOWNLOAD_MODE_DEFAULT
>>  config SYSFB
>>         bool
>>         default y
>> -       depends on X86 || ARM || ARM64 || RISCV || COMPILE_TEST
>> +       depends on X86 || EFI
> 
> Thanks, much better.
> Still, now this worm is crawling out of the X86 can, I'm wondering
> why this option is so important that it has to default to y?
> It is not just a dependency for SYSFB_SIMPLEFB, but also causes the
> inclusion of drivers/firmware/sysfb.c.
>

It defaults to yes because drivers/firmware/sysfb.c contains the logic
to register a "simple-framebuffer" device (or "efi-framebuffer" if the
CONFIG_SYSFB_SIMPLEFB Kconfig symbol is not enabled).

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.

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

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat