Document the color extension in Documentation/leds/leds-class.txt Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx> --- v2: - introduced to patch series v3: - document extension in more detail v4: - Better explain why flag LED_SET_HUE_SAT is needed v5: - no changes --- Documentation/leds/leds-class.txt | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt index d406d98..b1e4cba 100644 --- a/Documentation/leds/leds-class.txt +++ b/Documentation/leds/leds-class.txt @@ -8,6 +8,22 @@ LED is defined in max_brightness file. The brightness file will set the brightne of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware brightness support so will just be turned on for non-zero brightness settings. +If a driver uses the colour extension of the LED core then the brightness +file can be used to set hue / saturation / value. The brightness value is +interpreted as: <0000000F><HHHHHHHH><SSSSSSSS><VVVVVVVV> +Usage of the least byte is identical to monochrome mode. Saturation can be +0-255 and hue 0-251 (Colour circle is mapped to 0-252). +If hue and saturation both are 0 the current colour is preserved and only +the brightness is set. This ensures backwards compatibility with monochrome +mode, e.g. for led_set_brightness() calls from triggers. +However we might want to have the option to set all HSV components, even +if hue and saturation both are 0 (e.g. via brightness sysfs attribute). +Use case: Set color to white (hue = 0 and saturation = 0). +Therefore the default behaviour can be overridden with flag F (LED_SET_HUE_SAT). +If this flag is set then hue and saturation are not checked for being 0 and +the color components are set unconditionally. Example: +0x010000ff sets the LED to white color with full brightness. + The class also introduces the optional concept of an LED trigger. A trigger is a kernel based source of led events. Triggers can either be simple or complex. A simple trigger isn't configurable and is designed to slot into @@ -45,11 +61,12 @@ Is currently of the form: "devicename:colour:function" -There have been calls for LED properties such as colour to be exported as -individual led class attributes. As a solution which doesn't incur as much -overhead, I suggest these become part of the device name. The naming scheme -above leaves scope for further attributes should they be needed. If sections -of the name don't apply, just leave that section blank. +If the colour extension is used hsv / rgb can be used instead of a specific +colour. There have been calls for LED properties such as colour to be +exported as individual led class attributes. As a solution which doesn't +incur as much overhead, I suggest these become part of the device name. +The naming scheme above leaves scope for further attributes should they be +needed. If sections of the name don't apply, just leave that section blank. Brightness setting API -- 2.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
