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

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Message-ID: <52678D99.8090003@gmail.com>
Date:	Wed, 23 Oct 2013 16:49:29 +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 10/23/2013 04:00 PM, Thierry Reding wrote:
> On Wed, Oct 23, 2013 at 10:16:24AM +0800, Mark Zhang wrote:
>> 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.
> 
> If you automatically call backlight_update_status() everytime PRISM
> gives you new data, can't you just pass the correct value in in the
> first place so that you don't have to tweak it in the .notify()
> callback?

OK, how to do that? -- "pass the correct value in in the first place"?

Mark
> 
> Thierry
> 
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