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

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Date:   Tue, 27 Jul 2021 13:17:19 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
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

Hi Javier,

On Tue, Jul 27, 2021 at 12:22 PM Javier Martinez Canillas
<javierm@...hat.com> wrote:
> On 7/27/21 12:03 PM, Geert Uytterhoeven wrote:
> >> --- 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.

Do all (embedded) EFI systems have a frame buffer?

Perhaps SYSFB should be selected by SYSFB_SIMPLEFB, FB_VESA,
and FB_EFI?

> 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 ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds