On Thu, Feb 27, 2020 at 11:58:08AM +0100, Pavel Machek wrote: > Hi, Jacek! > > (and thanks for doing this). > > > We have here long lasting discussion related to LED multicolor class > > sysfs interface design. We went through several iterations and worked > > out the solution with individual file per each color sub-LED in the > > color directory as shown below: > > > > /sys/class/leds/<led>/colors/<color>_intensity > > > > This is in line with one-value-per-file sysfs rule, that is being > > frequently highlighted, and we even had not so long ago a patch > > for led cpu trigger solving the problem caused by this rule not > > being adhered to. > > Yep. One of the problems is that it is nice to change all the hardware > channels at once to produce color (it is often on i2c -- and slow), so > current proposals use "interesting" kind of latching. > > > Now we have the voice below bringing to attention another caveat > > from sysfs documentation: > > > > "it is socially acceptable to express an array of values of the same > > type" > > > > and proposing the interface in the form of two files: > > > > channel_intensity (file containing array of u32's) > > channel_names (usually containing "red green blue") > > And thus I want to have it in one file, so it is naturaly atomic. RGB > leds with 3 channels are common; I have not user yet, but there are > RGBW with 4 channels (and some more exotic stuff). I don't expect to > have more than 5 channels. Writing 3 or 4 or 5 numbers all at once in a single sysfs file to represent a single output should be fine. thanks, greg k-h
