Hi Rob, 2017-11-20 19:58 GMT+01:00 Rob Herring <robh@xxxxxxxxxx>: > On Thu, Nov 16, 2017 at 03:11:50PM +0100, Enric Balletbo i Serra wrote: >> Setting use-linear-interpolation in the dts will allow you to have linear >> interpolation between values of brightness-levels. >> >> There are now 256 between each of the values of brightness-levels. If >> something is requested halfway between 2 values, we'll use linear >> interpolation. >> >> This way a high resolution pwm duty cycle can be used without having to >> list out every possible value in the dts. > > I thought we already had a way to do that. > >> This system also allows for >> gamma corrected values (eg: "brightness-levels = <0 2 4 8 16 32>;"). >> >> Patch based on the Alexandru M Stan work done for ChromeOS kernels. >> >> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx> >> --- >> .../bindings/leds/backlight/pwm-backlight.txt | 2 + >> drivers/video/backlight/pwm_bl.c | 55 +++++++++++++++++----- >> include/linux/pwm_backlight.h | 2 + >> 3 files changed, 47 insertions(+), 12 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> index 764db86..7c48f20 100644 >> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> @@ -17,6 +17,8 @@ Optional properties: >> "pwms" property (see PWM binding[0]) >> - enable-gpios: contains a single GPIO specifier for the GPIO which enables >> and disables the backlight (see GPIO binding[1]) >> + - use-linear-interpolation: set this propriety to enable linear interpolation >> + between each of the values of brightness-levels. > > Isn't this really just whether you allow values not listed because what > other kind of interpolation would you do? Yes, the idea behind this is just allow values not listed. > Seems like you should just be > able to query the resolution of the PWM and decide if it can take more > values than listed. > Without using a new DT propriety and let decide the driver when use intepolation and when not? Shouldn't this break current behavior then? You can have a high resolution PWM but I'm not sure if you want allow always more values than listed. Regards, Enric > Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
