linux-kernel - Re: [PATCH v2 1/2] fbdev: Split frame buffer support in FB and FB

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Message-ID: <873525e8tb.fsf@minerva.mail-host-address-is-not-set>
Date:   Mon, 03 Jul 2023 09:46:40 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, linux-fbdev@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helge Deller <deller@....de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v2 1/2] fbdev: Split frame buffer support in FB and
 FB_CORE symbols

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

Hello Thomas,

Thanks for your review.

> Hi
>
> Am 01.07.23 um 23:44 schrieb Javier Martinez Canillas:

[...]

>>   
>> +menuconfig FB_CORE
>> +	tristate "Core support for frame buffer devices"
>
> With the text, this is visible; as others noted.
>

Yes, I misremembered what made a Kconfig symbol non-visible, and thought
that was just the lack of a help section but forgot to remove the prompt.

This is already fixed in v3.

>> +
>>   menuconfig FB
>> -	tristate "Support for frame buffer devices"
>> +	tristate "Support for frame buffer device drivers"
>
> Just keep the text as-is.
>

I disagree. Because we are slightly changing the Kconfig symbol semantics
here, for instance CONFIG_FB_CORE + CONFIG_DRM_FBDEV_EMULATION will also
provide a frame buffer device (and with CONFIG_FB_DEVICE, will be exposed
to user-space as a /dev/fb? device).

So now CONFIG_FB is really about allowing the native fbdev drivers to be
enabled. That's why I'm changing the prompt text to make that more clear.

[...]

>>   config FB_DEVICE
>>   	bool "Provide legacy /dev/fb* device"
>> -	depends on FB
>> +	select FB_CORE
>
> This should depend on FB_CORE.
>

Yes, already fixed in v3 too. I did a select to prevent symbol circular
dependencies but doing that lead to CONFIG_FB_CORE=y even if CONFIG_DRM
was set as a module.

But with the "select FB_CORE if DRM_FBDEV_EMULATION" in the DRM symbol as
Arnd suggested, I was able to have FB_DEVICE to depend on FB_CORE again.

> Best regards
> Thomas
>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat