On Fri, 12 Mar 2021 08:48:55 +0000 Hermes Zhang <Hermes.Zhang@xxxxxxxx> wrote: > Hi Alexander, > > > Am Donnerstag, 11. März 2021, 14:04:08 CET schrieb Hermes Zhang: > > > From: Hermes Zhang <chenhuiz@xxxxxxxx> > > > > > > Introduce a new Dual GPIO LED driver. These two GPIOs LED will act as > > > one LED as normal GPIO LED but give the possibility to change the > > > intensity in four levels: OFF, LOW, MIDDLE and HIGH. > > > > Interesting use case. Is there any real world hardware wired like that you > > could point to? > > > > Yes, we have the HW, it's not a chip but just some circuit to made of. > > > > +config LEDS_DUAL_GPIO > > > + tristate "LED Support for Dual GPIO connected LEDs" > > > + depends on LEDS_CLASS > > > + depends on GPIOLIB || COMPILE_TEST > > > + help > > > + This option enables support for the two LEDs connected to GPIO > > > + outputs. These two GPIO LEDs act as one LED in the sysfs and > > > + perform different intensity by enable either one of them or both. > > > > Well, although I never had time to implement that, I suspect that could > > conflict if someone will eventually write a driver for two pin dual color LEDs > > connected to GPIO pins. We actually do that on our hardware and I know > > others do, too. > > > > I asked about that back in 2019, see this thread: > > > > https://www.spinics.net/lists/linux-leds/msg11665.html > > > > At the time the multicolor framework was not yet merged, so today I would > > probably make something which either uses the multicolor framework or at > > least has a similar interface to userspace. However, it probably won't surprise > > you all, this is not highest priority on my ToDo list. ;-) > > > > (What we actually do is pretend those are separate LEDs and ignore the > > conflicting case where both GPIOs are on and the LED is dark then.) > > > > Yes, that case seems conflict with mine, the pattern for me is like: > > P1 | P2 | LED > -- + -- + ----- > 0 | 0 | off > 0 | 1 | Any color > 1 | 0 | Any color > 1 | 1 | both on > > Now I'm investigate another way from Marek's suggestion by using REGULATOR_GPIO, to see if could meet my requirement. If yes, then I do think no new driver is needed. Maybe you could even implement multicolor-gpio, now that we have multicolor LED class :) Marek
