On Thu, May 19, 2022 at 04:00:02PM -0700, Douglas Anderson wrote: > Like many i2c-hid touchscreen controllers, the Elan eKTH6915 > controller has a reset gpio. For the Goodix GT7375P touchscreen the > decision was to add a new binding rather than trying to add a new GPIO > to the existing i2c-hid binding. We'll follow the lead and do it here, > too. > > SIDE NOTE: the Elan eKTH6915 is a touchscreen _controller_ that's > included as a part on some touchscreens. The reset line isn't truly > necessary for the functioning of the touchscreen, so it's possible > that some designs won't have it hooked up and will just guarantee the > power sequencing requirements with RLC circuits. Thus, we'll mark the > reset gpio as optional. > > Note that if the reset GPIO isn't used there's actually no true need > to use the "elan,ekth6915" compatible instead of the "hid-over-i2c" on > Linux. However: > - Officially using just "hid-over-i2c" for this device violates the > existing "hid-over-i2c" bindings. The bindings say that you're not > supposed to use "post-power-on-delay-ms" without specifying a more > specific compatible. Currently the Linux driver doesn't enforce > this, but it violates the bindings to just use > "hid-over-i2c". ...and if you're going to add a more specific > compatible anyway, might as well do it right. > - Using this compatible means we don't need to specify > "hid-descr-addr" since it's inferred from the compatible. > - Using this compatible means that the regulator names match the names > on the Elan datasheet (vcc33 / vccio) vs the generic hid-over-i2c > (vdd / vddl). > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> Thanks. -- Dmitry
