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

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Date:	Fri, 18 Oct 2013 12:48:12 +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 10/17/2013 03:14 PM, Thierry Reding wrote:
> On Thu, Oct 17, 2013 at 02:49:57PM +0800, Mark Zhang wrote:
>> Hi,
>>
>> This is the first time I send mail to linux-pwm, I didn't read through
>> the mails in this list, so if somebody already asked this question, I'm
>> sorry about that.
>>
>> I wanna set some fops in "struct platform_pwm_backlight_data". But the
>> currrent probe function in pwm_bl.c says:
>>
>> -------
>> if (!data) {
>> 	ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
>> 	if (ret < 0) {
>> 		dev_err(&pdev->dev, "failed to find platform data\n");
>> 		return ret;
>> 	}
>>
>> 	data = &defdata;
>> }
>> -------
>>
>> This looks like if we set the platform data for pwm backlight device,
>> "pwm_backlight_parse_dt" will never have a chance to be called, which
>> means the stuffs I defined in backlight DT node will be ignored.
>>
>> If I don't set the platform data for pwm backlight device, according to
>> the pwm_backlight_probe, I will never have a chance to set some fops
>> which I need(like "notify", "check_fb"...).
>>
>> So, what I suppose to do now? Maybe there is a way to set function
>> pointers in DT?
> 
> Perhaps you could describe in more detail what you need the functions
> for.
> 

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.

Mark
> Generally you're not supposed to mix DT and platform data. Without more
> info that's about all I can say.
> 
> Thierry
> 
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