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

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sam,

On Sat, Mar 07, 2020 at 09:08:13PM +0100, Sam Ravnborg wrote:
> On Fri, Mar 06, 2020 at 04:18:52PM +0100, Thomas Zimmermann wrote:
> > Am 06.03.20 um 15:22 schrieb Laurent Pinchart:
> > > 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@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.
> 
> 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()

Or better, rename the existing drm_encoder_init() to
drm_encoder_init_funcs(), and rename drm_simple_encoder_init() to
drm_encoder_init() ? It's the common case.

> 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@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.

-- 
Regards,

Laurent Pinchart
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