[PATCH] fbdev: udl: Make CONFIG_FB_DEVICE optional

[Thomas Zimmermann]

Hi

Am 30.10.24 um 10:30 schrieb Helge Deller:

>>>
>>> I'm happy to get rid of the fbdev drivers, but for that DRM really 
>>> needs
>>> to allow some sort of native fillrect, copyarea and imageblt 
>>> operations so
>>> that we can get performance back on the old cards when implementing 
>>> them
>>> as DRM driver.
>>
>> This is unrelated to udl.
>
> No, it's not.
> The udl fbdev driver implements those functions (like the other fbdev 
> drivers)
> and as such fbcon on top of udl is accelerated, while fbcon on drm 
> drivers
> is unaccelerated.

Udlfb uses the regular software implementations to draw into its shadow 
buffer. It then schedules an update to copy the update over USB to the 
adapter's internal framebuffer memory. [1] Udl uses exactly the same 
code pattern and most of the involved helpers. [2]

[1] 
https://elixir.bootlin.com/linux/v6.11.5/source/drivers/video/fbdev/udlfb.c#L1145
[2] 
https://elixir.bootlin.com/linux/v6.11.5/source/drivers/gpu/drm/drm_fbdev_shmem.c#L39

Best regards
Thomas

>
> Helge

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)