Re: [PATCH] drm/todo: Drop todo item to request memory regions in all fbdev drivers

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 23.04.26 um 22:55 schrieb Helge Deller:
> This item is tagged for beginners, so often people not familiar with
> the fbdev drivers think this is an easy task, start up their AI tools
> and blindly send in the generated code as patches.
>
> The problem:
> - Those patches often introduce bugs, so
> - ideally want the code tested, since ressource misconfigurations
>    often lead to failing drivers
> - The patches are often unnecessary, since in the old machines with the
>    old graphic cards resource conflicts usually don't happen as only one
>    graphic card can be used at a time anyway.
> - and today most relevant drivers have necessary patches already
>    implemented.
>
> So, let's get rid of this todo item and silence the steady stream of
> stupid patches.

I see that AI patches can be problematic, but reserving these regions is 
still the correct thing to do. Removing the TODO item will not change that.

Some background on why this item exists: we currently use aperture 
helpers [1] to manage ownership of the framebuffer memory during boot 
up. This is necessary to switch from the system-framebuffer driver 
(i..e, simplefb, simpledrm, etc) to the hardware's native driver. But 
this is all ad-hoc because Linux' resource management doesn't do this 
for us. Before we can integrate any such functionality, we have to fix 
all drivers to reserve their resources correctly.

If we remove the TODO item, we'd likely still want to move forward with 
improving resource management. If that breaks unfixed fbdev drivers, 
users would then also send bug reports.

And the other point is (again) that if there are no means of testing a 
driver and no information whether a driver is actually in used by 
anyone, it's maybe time to remove the driver.

[1] 
https://elixir.bootlin.com/linux/v7.0.1/source/drivers/video/aperture.c#L17

Best regards
Thomas


>
> Signed-off-by: Helge Deller <deller@gmx.de>
> ---
>   Documentation/gpu/todo.rst | 16 ----------------
>   1 file changed, 16 deletions(-)
>
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index bc9f14c8a2ec..b4dd64a8cc06 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -448,22 +448,6 @@ Contact: Thomas Zimmermann <tzimmermann@suse.de>
>   
>   Level: Intermediate
>   
> -Request memory regions in all fbdev drivers
> ---------------------------------------------
> -
> -Old/ancient fbdev drivers do not request their memory properly.
> -Go through these drivers and add code to request the memory regions
> -that the driver uses. This requires adding calls to request_mem_region(),
> -pci_request_region() or similar functions. Use helpers for managed cleanup
> -where possible. Problematic areas include hardware that has exclusive ranges
> -like VGA. VGA16fb does not request the range as it is expected.
> -Drivers are pretty bad at doing this and there used to be conflicts among
> -DRM and fbdev drivers. Still, it's the correct thing to do.
> -
> -Contact: Thomas Zimmermann <tzimmermann@suse.de>
> -
> -Level: Starter
> -
>   Remove driver dependencies on FB_DEVICE
>   ---------------------------------------
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)