Re: [RFC PATCH 0/3] drm/panel: Pull some code out into common helpers

From: Sean Paul <seanpaul@chromium.org>
To: Emil Velikov <emil.l.velikov@gmail.com>
Cc: ML dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [RFC PATCH 0/3] drm/panel: Pull some code out into common helpers
Date: Wed, 22 Mar 2017 11:06:25 -0400	[thread overview]
Message-ID: <20170322150625.GP19389@art_vandelay> (raw)
In-Reply-To: <CACvgo52qTw6zx3BgFDSpuvNKKAO4Vd3UDTN8bRW33rFK1=GZfA@mail.gmail.com>

On Wed, Mar 22, 2017 at 02:36:27PM +0000, Emil Velikov wrote:
> Hi Sean,
> 
> On 16 March 2017 at 22:08, Sean Paul <seanpaul@chromium.org> wrote:
> > This series pulls out the power-sequencing code from panel-simple into a
> > panel-common helper library. This allows drivers that cannot leverage
> > panel-simple to share some code.
> >
> > I've converted the 2 sharp mipi drivers, and Chris Zhong's driver on the
> > list can also be converted. I haven't checked any other drivers, but I
> > suspect we'll see the same code blocks there too.
> >
> > I'm sure there's more we can pull out of the various drivers, but this
> > seems like a good place to start talking about how to share common panel
> > code across drivers.
> >
> Fwiw I think that the idea is good, but I'm wondering on the following
> architectural questions:

Hey Emil,
Thanks for your feedback!

>  - Shouldn't prepared and enabled be part of struct drm_panel ?

I don't think so. Not all panels need to worry about keeping track of the
prepared/enabled state.

>  - Would it be better to subclass struct panel_common around struct drm_panel ?
> 
> I might be threading the thin line of "midlayer vs helpers" here, so
> please let me know if I've got it wrong.

Yeah, you could do either. I was going for something more akin to the helpers we
already have. If you went the subclass route, the drivers would need to subclass
panel_common, which would subclass drm_panel. I figured it was too much
unraveling to get at the important bits in the hooks that provide a drm_panel
pointer. Nothing that a few to_* helpers couldn't solve, though.

I was also thinking we could subclass panel_common if there's an opportunity to
get something like mipi_dcs_panel_common to reduce the copypasta amongst mipi
panels which execute a common dcs recipe.

Sean

> 
> Thanks
> Emil

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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