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From: Javier Martinez Canillas <javierm@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>, Mehdi Djait
 <mehdi.djait.k@gmail.com>, daniel@ffwll.ch,
 maarten.lankhorst@linux.intel.com, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org
Subject: Re: drm/tiny: QUESTION: What to use instead of
 drm_simple_display_pipe ?
In-Reply-To: <da7cfff1-e147-48ea-bcda-9ea913e5feee@suse.de>
References: <ZfiTbYAa7qxXlrPd@mehdi-archlinux>
 <da7cfff1-e147-48ea-bcda-9ea913e5feee@suse.de>
Date: Tue, 19 Mar 2024 09:52:34 +0100
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Thomas Zimmermann <tzimmermann@suse.de> writes:

Hello Mehdi,

> 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@b=
ootlin.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=
=20
> and start inlining everything. For example
>
>  =C2=A01) Your driver calls drm_simple_display_pipe_init(), so you copy t=
hat=20
> code into your source file
>  =C2=A02) drm_simple_display_pipe_init() uses drm_simple_kms_plane_funcs =
and=20
> drm_simple_kms_crtc_funcs, so you copy these into your source file;=20
> together with the drm_simple_kms_*() helpers that they use for their=20
> callback pointers.
>  =C2=A03) Mayb do this for other drm_simple_kms_*() code.
>  =C2=A04) Then start inlining: inline your copy of=20
> drm_simple_display_pipe_iit(). Instead of using=20
> sharp_ls027b7dh01_pipe_funcs, inline its functions into your copy of the=
=20
> callers. And so on.
>  =C2=A05) Rename the resulting code, so that it fits you driver.
>
> With careful changes, you 'll end up with the same functionality as=20
> before, but without the intermediate layer of the simple-KMS code.
>

On top of what Thomas said, you can check 622113b9f11f ("drm/ssd130x:
Replace simple display helpers with the atomic helpers") that did this
change for the drivers/gpu/drm/solomon/ssd130x.c driver.

The driver is also for a monochrome panel controller and it does support
SPI as transport, which means the controller is similar to yours in many
aspects. You could use that driver code as a reference for your driver.

> Best regards
> Thomas
>
>>
>> --
>> Kind Regards
>> Mehdi Djait
>
> --=20
> --
> 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)
>

--=20
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat