linux-kernel - Re: [PATCH v2] pwm-backlight: allow for non-increasing brightness levels

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Date:	Fri, 27 Sep 2013 12:28:21 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Tomi Valkeinen' <tomi.valkeinen@...com>,
	'Thierry Reding' <thierry.reding@...il.com>
Cc:	'Mike Dunn' <mikedunn@...sguy.com>,
	'Richard Purdie' <rpurdie@...ys.net>,
	'Jean-Christophe Plagniol-Villard' <plagnioj@...osoft.com>,
	'Grant Likely' <grant.likely@...aro.org>,
	'Rob Herring' <rob.herring@...xeda.com>,
	linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	'Robert Jarzmik' <robert.jarzmik@...e.fr>,
	'Marek Vasut' <marex@...x.de>,
	'Laurent Pinchart' <laurent.pinchart+renesas@...asonboard.com>,
	'Jingoo Han' <jg1.han@...sung.com>
Subject: Re: [PATCH v2] pwm-backlight: allow for non-increasing brightness
 levels

On Thursday, September 26, 2013 9:08 PM, Tomi Valkeinen wrote:
> On 26/09/13 14:51, Thierry Reding wrote:
> > On Thu, Sep 26, 2013 at 01:03:06PM +0300, Tomi Valkeinen wrote:
> > [...]
> >> But if you and Thierry think this version is good, I'll take it.
> >
> > That sounds like you want to take it through the fbdev tree. Jingoo is
> > listed (along with Richard, but he hasn't been responsive to email for
> > years) as maintainer for the backlight subsystem. Furthermore back at
> 
> Ah, so they are. I just thought it falls under fbdev, as it's under
> drivers/video/ =).
> 
> I don't have any particular "want" to take it through fbdev tree. But I
> can take it.
> 
> > the time when I began working on the PWM subsystem, the backlight sub-
> > system was pretty much orphaned, and pwm-backlight was by far the
> > biggest user of the PWM subsystem. I adopted the driver at the time
> > because it needed to be updated for PWM subsystem changes.
> >
> > What's the plan going forward? Given the coupling between the PWM
> > subsystem and the pwm-backlight driver it might be useful to keep
> > maintaining it as part of the PWM subsystem. On the other hand, there's
> > some coupling between the driver and the backlight subsystem too.
> 
> And backlight is coupled with fbdev... Which is something I don't like.

+cc Laurent Pinchart,

Yes, right. 
The backlight should be de-coupled with fbdev.
I remember that Laurent Pinchart was doing this patch.

Laurent Pinchart,
Would you let us know your plan about this? :-)

> 
> > I have a couple of patches queued up for 3.13 that rework parts of the
> > driver, so it'd be good to know how you guys want to handle this.
> 
> Well. I'm happy if somebody wants to maintain the backlight side. In
> fact, I'd be happy if somebody would start restructuring it totally,
> it's rather messy. The link with fbdev should be removed, and some
> backlight drivers are actually panel drivers. However, perhaps Common
> Display Framework is required until it can be fully cleaned.

I think that some backlight drivers can be moved to 'Common Display Framework',
after 'Common Display Framework' is merged.
But, I am not sure, when it will be completed.

Best regards,
Jingoo Han

> 
> So... For the time being, I'm fine with merging pwm-backlight via any
> tree that works best. I'm presuming here that backlight framework and
> fbdev (for the parts that are relevant for backlight) are not really
> being changed, so there shouldn't be conflicts.
> 
>  Tomi
> 

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