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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <b8472f68-982b-c00b-55cc-547c72bef34c@redhat.com>
Date: Fri, 10 Oct 2025 17:11:49 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Thomas Zimmermann <tzimmermann@...e.de>
cc: Helge Deller <deller@....de>, sukrut heroorkar <hsukrut3@...il.com>, 
    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 Tue, 7 Oct 2025, Thomas Zimmermann wrote:

> Hi
> 
> Am 03.10.25 um 21:50 schrieb Helge Deller:
> > 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].

It was me - and I am still using it on an ARM64 MacchiatoBIN board because 
the board doesn't have graphics output.

The problems with the UDL DRM driver were:

* crashes with full-screen framebuffer applications, such as "links2 -g", 
"fbi" or "fbgs". On UDLFB, there are no crashes.

* worse performance - the UDL DRM driver updates everything in a given 
rectangle, while the UDLFB driver keeps back-buffer and front-buffer and 
updates only differences between them.

* crash when you unplug the card while Xorg was running (already fixed)

Mikulas