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(). > The param of "backlight_update_status" is "struct backlight_device *". So you mean after I get a pointer of correct backlight device, just set the brightness value I want to it's "props.brightness" directly? I think the "struct backlight_device" should be opaque(although it's definition is in include/linux/backlight.h, I know that), so it's better not to touch it's member directly, that's why I wanna use that "notify" callback. Mark > Thierry > -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
