linux-kernel - Re: [PATCH] fbdev: udlfb: make CONFIG_FB

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Message-ID: <c1d86274-44e2-4ceb-b887-5c4af45d8b37@gmx.de>
Date: Fri, 3 Oct 2025 21:50:01 +0200
From: Helge Deller <deller@....de>
To: sukrut heroorkar <hsukrut3@...il.com>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 Mikulas Patocka <mpatocka@...hat.com>
Cc: David Hunter <david.hunter.linux@...il.com>,
 kernel test robot <lkp@...el.com>, Bernie Thompson <bernie@...gable.com>,
 Arnd Bergmann <arnd@...db.de>, Randy Dunlap <rdunlap@...radead.org>,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
 Zsolt Kajtar <soci@....rulez.org>,
 Gonzalo Silvalde Blanco <gonzalo.silvalde@...il.com>,
 linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
 oe-kbuild-all@...ts.linux.dev, skhan@...uxfoundation.org
Subject: Re: [PATCH] fbdev: udlfb: make CONFIG_FB_DEVICE optional

On 10/3/25 20:43, sukrut heroorkar wrote:
> On Thu, Oct 2, 2025 at 8:52 AM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>> Am 02.10.25 um 08:41 schrieb Helge Deller:
>>>>>> kernel test robot noticed the following build errors:
>>>>>
>>>>> Did you compile and test this code before submitting this patch?
>>>>
>>>> Yes, I had compiled & loaded the udlfb module with no errors. Please
>>>> let me know how to proceed in this case.
>>>
>>> Look at the reported build error, which seems to happen in dev_dbg().
>>> So, maybe in your testing you did not have debugging enabled?
>>> The report contains the .config file with which you can test.
>>
>> Can we rather make an effort to remove the udlfb driver entirely? A few
>> years back, there was one user who was still using it because of some
>> problems with the DRM udl driver. But I think we've addressed them. The
>> discussion is at [1].

Would be good to know if they issues/crashes really have been solved.
In [1] it seems the crashes still happened with DRM.

> Should I send a patch series to completely remove udlfb, 

No. (at least not yet)

> since [1] echoed that DRM udl driver is good enough?
>> [1] https://lore.kernel.org/dri-devel/20201130125200.10416-1-tzimmermann@suse.de/

Well, some people who do *NOT* actively use fbdev with the old
cards say the DRM replacements are "good enough".
For tThose people who really depend on fbdev and the speed it has
over DRM, the DRM "basic-drivers" are simply a nice-to-have-but-not-really-useable
type of drivers.
So, unless the really affected people say the DRM replacement
is fully usable, we need to keep the fbdev driver.

Helge