Bug#840897: general: framebuffer modules for non-dri graphics cards are not loaded

[Michael Biebl]

Am 01.09.20 um 19:43 schrieb Ben Hutchings:
> On Sun, 30 Aug 2020 19:08:00 +0200 Michael Biebl <biebl at debian.org> wrote:
>> Control: reassign -1 udev
>> Control: tags -1 + moreinfo
>>
>> Am 30.08.20 um 12:21 schrieb Chris Hofstaedtler:
>>> Control: reassign -1 systemd
>>>
>>> * Michal Suchanek <hramrach at gmail.com>:
>>>> So I would like the fbdev modules removed from whatever blacklist prevents
>>>> loading them and have them loaded on systems that don't have dri modules to
>>>> handle graphics.
>>>
>>> AFAICT systemd ships the fbdev blacklist nowadays, reassigning
>>> there.
>>
>> The udev package does (but it's src:systemd, so close enough) in
>> /lib/modprobe.d/fbdev-blacklist.conf
>>
>> I don't know the history behind this file though, it predates the
>> udev/systemd merge and a quick search in the old src:udev package did
>> not really yield anything useful.
>>
>> Hopefully Marco can chime in here and provide some context why it was
>> added and if it's still required thoday.
> 
> The old-style fbdev drivers generally cannot coexist with user-mode
> graphics drivers or DRM drivers for the same devices (but the latter
> can coexist with each other).  The fbdev API provides very little
> opportunity for X graphics acceleration, so it's generally preferable
> to use X with user-mode graphics drivers (or the newer combined DRM/KMS
> drivers).  Therefore the fbdev drivers were blocked from auto-loading
> by default.

Thanks for this additional information, Ben.

> I believe this file used to be a conffile in /etc so that it was
> possible to override it in case the user prefers the fbdev driver.

You can still do that by creating a file
/etc/modprobe.d/fbdev-blacklist.conf which will override the one from /lib.

> This does not explain why listing atyfb in a modules list does not
> work; the "blacklist" directive should not affect that.

Maybe the user did not rebuild his initramfs and the initramfs already
loaded the non-fb driver, so loading fbdev failed?

Michal, can you still reproduce the problem after running
update-initramfs -u ?

Michael

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