On Wed, Oct 23, 2013 at 06:46:17PM +0800, Mark Zhang wrote: > On 10/23/2013 06:36 PM, Mark Zhang wrote: > > On 10/23/2013 05:09 PM, Thierry Reding wrote: > >> On Wed, Oct 23, 2013 at 04:49:29PM +0800, Mark Zhang wrote: > >>> 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"? > >> > >> Well, if you call backlight_update_status(), then you can pass in a > >> brightness value, right? You usually do that by setting the backlight's > >> props.brightness field. > >> > >> So when PRISM gives you new data, you could just read out the current > >> brightness, compute the new one based on the current one and the PRISM > >> data, set the props.brightness field to that value and then call > >> backlight_update_status(). > >> > > > > Okay, anyway, I got the idea. Actually it's simpler. :) > > I'm just curious that if we can do that in this way, why we need > > "notify" anymore? > > Oh, by the way, how about "check_fb" fops? Is there some kind of > substitution as well? I mean, if I wanna set "check_fb" and also want to > define the backlight device via DT, is there a way to do that? No, there's no substitution for that. .check_fb() is used to verify that a backlight device is associated with a framebuffer device. There are better ways to check for that with DT, although nothing has been merged into mainline yet. Thierry
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