linux-kernel - Re: [PATCH] drm: Drop select FRAMEBUFFER_CONSOLE for DRM_FBDEV

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Message-Id: <19a2a2a0-2f35-4c4e-926c-47b75e6f9353@app.fastmail.com>
Date:   Fri, 04 Aug 2023 15:51:40 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Daniel Vetter" <daniel@...ll.ch>,
        "Javier Martinez Canillas" <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        "Arthur Grillo" <arthurgrillo@...eup.net>,
        "Randy Dunlap" <rdunlap@...radead.org>,
        "Dave Airlie" <airlied@...il.com>, "Helge Deller" <deller@....de>,
        "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
        "Maxime Ripard" <mripard@...nel.org>,
        "Thomas Zimmermann" <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm: Drop select FRAMEBUFFER_CONSOLE for DRM_FBDEV_EMULATION

On Fri, Aug 4, 2023, at 15:07, Daniel Vetter wrote:
> On Fri, 4 Aug 2023 at 14:52, Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>>
>> The commit c242f48433e7 ("drm: Make FB_CORE to be selected if DRM fbdev
>> emulation is enabled") changed DRM_FBDEV_EMULATION from 'depends on FB'
>> to an effective 'select FB_CORE', so any config that previously had DRM=y
>> and FB=n now has FB_CORE=y and FRAMEBUFFER_CONSOLE=y.
>>
>> This leads to unmet direct dependencies detected for FRAMEBUFFER_CONSOLE
>> as reported by Arthur Grillo, e.g:
>>
>> WARNING: unmet direct dependencies detected for FRAMEBUFFER_CONSOLE
>>   Depends on [n]: VT [=n] && FB_CORE [=y] && !UML [=y]
>>   Selected by [y]:
>>   - DRM_FBDEV_EMULATION [=y] && HAS_IOMEM [=y] && DRM [=y] && !EXPERT [=n]
>>
>> Arnd Bergmann suggests to drop the select FRAMEBUFFER_CONSOLE for the
>> DRM_FBDEV_EMULATION Kconfig symbol, since a possible use case could
>> be to enable DRM fbdev emulation but without a framebuffer console.
>>
>> Fixes: c242f48433e7 ("drm: Make FB_CORE to be selected if DRM fbdev emulation is enabled")
>> Reported-by: Arthur Grillo <arthurgrillo@...eup.net>
>> Closes: https://lore.kernel.org/dri-devel/20230726220325.278976-1-arthurgrillo@riseup.net
>> Suggested-by: Arnd Bergmann <arnd@...db.de>
>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>
> Yeah originally this was just to help people not misconfigure their
> kernels and end up with a black screen. But select is really not a
> nice way to do that, imo we could drop the FB_CORE select too :-)

Droping the 'FB_CORE' select only works if we make FB_CORE user
visible and add a 'depends on' for it instead. Not sure this
is any better since this would only ever be used when either
CONFIG_FB or CONFIG_DRM_FBDEV_EMULATION is enabled.


     Arnd