linux-kernel - Re: How to set fops in "struct platform_pwm_backlight

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Message-ID: <52673178.8070805@gmail.com>
Date:	Wed, 23 Oct 2013 10:16:24 +0800
From:	Mark Zhang <nvmarkzhang@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	rpurdie@...ys.net, jg1.han@...sung.com,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	tomi.valkeinen@...com, linux-pwm@...r.kernel.org,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: How to set fops in "struct platform_pwm_backlight_data"?

On 10/22/2013 08:49 PM, Thierry Reding wrote:
> On Tue, Oct 22, 2013 at 04:55:09PM +0800, Mark Zhang wrote:
>> On 10/22/2013 03:24 PM, Thierry Reding wrote:
>>> On Fri, Oct 18, 2013 at 12:48:12PM +0800, Mark Zhang wrote:
>> [...]
>>>>>
>>>>
>>>> Okay, I just want to set the "notify" function pointer in "struct
>>>> platform_pwm_backlight_data", because I want to tune the brightness
>>>> value before the pwm-bl sets the brightness to hardware. I don't know
>>>> how to do that, unless we define the platform data explicitly.
>>>
>>> Okay, my question should have been what you need the functions for and
>>> why you think you need them.
>>>
>>
>> If I understanding you correctly, I suppose I've said that: "because I
>> want to tune the brightness value before the pwm-bl sets the brightness
>> to hardware".
> 
> Why do you want to tune the brightness value? What are you trying to
> achieve?
> 

Oh, Tegra has a feature named PRISM(aka SmartDimmer). It changes the
color value to make the display looks bright so that we can reduce the
backlight brightness to save power. So everytime PRISM is triggered, we
call "backlight_update_status", then in the "notify" callback, we change
the brightness value which pwm-bl provides by considering the PRISM
compensations.

Mark
> Thierry
> 
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