[PATCH 00/22] drm: Convert drivers to drm_simple_encoder_init()

[Thomas Zimmermann]

Hi Sam

Am 07.03.20 um 21:08 schrieb Sam Ravnborg:
> Hi Thomas.
> 
> On Fri, Mar 06, 2020 at 04:18:52PM +0100, Thomas Zimmermann wrote:
>> Hi Laurent
>>
>> Am 06.03.20 um 15:22 schrieb Laurent Pinchart:
>>> Hi Thomas,
>>>
>>> Thank you for the patch.
>>>
>>> On Thu, Mar 05, 2020 at 04:59:28PM +0100, Thomas Zimmermann wrote:
>>>> A call to drm_simple_encoder_init() initializes an encoder without
>>>> further functionality. It only provides the destroy callback to
>>>> cleanup the encoder's state. Only few drivers implement more
>>>> sophisticated encoders than that. Most drivers implement such a
>>>> simple encoder and can use drm_simple_encoder_init() instead.
>>>>
>>>> The patchset converts drivers where the encoder's instance is
>>>> embedded in a larger data structure. The driver releases the
>>>> memory during cleanup. Each patch replaces drm_encoder_init() with
>>>> drm_simple_encoder_init() and removes the (now unused) driver's
>>>> encoder functions.
>>>>
>>>> While the patchset is fairly large, the indiviual patches are self-
>>>> contained and can be merged independently from each other. The
>>>> simple-encoder functionality is currently in drm-misc-next, where
>>>> these patches could go as well.
>>>
>>> I've reviewed the whole series, including verifying that the few
>>> instances of struct drm_encoder_funcs that were not declared const were
>>> not modified somewhere to add more function pointers.
>>>
>>> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>>
>> Thanks for the detailed review.
>>
>>>
>>> for all the patches.
>>>
>>> However, I'd like to note that drm_simple_encoder_init() is a bit of a
>>> misnommer here. Several of the encoders in those drivers to implement
>>> additional functionality. They just expose them through
>>> drm_encoder_helper_funcs, not drm_encoder_funcs.
>>
>> True. It's called 'simple encoder' for the lack of a better name. It's
>> part of the simple KMS helpers, so the name's at least consistent. OTOH
>> I always find drm_simple_display_pipe a bad name.
>>
>> We can still rename the simple-encoder function without much effort. I'm
>> open for suggestions.
> 
> IMO this does not belong in drm_simple_kms - but in drm_encoder.
> This only occurs to me after looking a bit more on the patches,
> you would have loved to get this feedback earlier.

Well, the simple-encoder functionality used to be located in the encoder
code, but Daniel mentioned this is more of a helper and asked me to move
it out of the core. [1] So it ended up with the simple-KMS helpers.

Best regards
Thomas

[1] https://patchwork.freedesktop.org/patch/352370/?series=73130&rev=1

> 
> Most users do not need their owm drm_encoder_funcs definition,
> and would be happy with the default as provided by drm_simple_*
> 
> As the cleanup is handled automatically when the drm device
> is teared down (in mode_config_rest()) I considered if we could here
> use the drmm_ namespace - but that felt wrong.
> 
> My proposal is the following:
> - Move the implementation to drm_encoder.c
> - Name it drm_encoder_init_nofuncs()
> 
> The patches posted in this thread would be a little simpler
> as they would loose the added include file.
> And the three drivers using the current infrastructure would need a
> small update.
> 
> I you decide to keep the current approach where the
> functions are in drm_simple_* then the full series is:
> Acked-by: Sam Ravnborg <sam at ravnborg.org>
> 
> But I think moving it to drm_encoder.c would be the approach that would
> make it simpler to understand/follow. So that get my (biased) vote.
> 
> 	Sam
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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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