linux-kernel - Re: drm/tiny: QUESTION: What to use instead of drm_simple_display

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Message-ID: <da7cfff1-e147-48ea-bcda-9ea913e5feee@suse.de>
Date: Tue, 19 Mar 2024 09:35:48 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Mehdi Djait <mehdi.djait.k@...il.com>, daniel@...ll.ch,
 maarten.lankhorst@...ux.intel.com, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: drm/tiny: QUESTION: What to use instead of
 drm_simple_display_pipe ?

Hi

Am 18.03.24 um 20:18 schrieb Mehdi Djait:
> Hello everyone :)
>
> I am implementing a tiny drm driver and I am currently working on the
> V2: https://lore.kernel.org/dri-devel/cover.1701267411.git.mehdi.djait@bootlin.com/
>
> I got a review on the v1 telling me not to use the
> drm_simple_display_pipe. Can someone please explain this further ? Or
> give me an example drm driver that does it the right way ?

You can copy the code from drm_simple_kms_helper.c into your driver file 
and start inlining everything. For example

  1) Your driver calls drm_simple_display_pipe_init(), so you copy that 
code into your source file
  2) drm_simple_display_pipe_init() uses drm_simple_kms_plane_funcs and 
drm_simple_kms_crtc_funcs, so you copy these into your source file; 
together with the drm_simple_kms_*() helpers that they use for their 
callback pointers.
  3) Mayb do this for other drm_simple_kms_*() code.
  4) Then start inlining: inline your copy of 
drm_simple_display_pipe_iit(). Instead of using 
sharp_ls027b7dh01_pipe_funcs, inline its functions into your copy of the 
callers. And so on.
  5) Rename the resulting code, so that it fits you driver.

With careful changes, you 'll end up with the same functionality as 
before, but without the intermediate layer of the simple-KMS code.

Best regards
Thomas

>
> --
> Kind Regards
> Mehdi Djait

-- 
--
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)