On Thu, Nov 21, 2013 at 11:34 AM, boris brezillon <b.brezillon@xxxxxxxxxxx> wrote: > On 21/11/2013 10:48, Linus Walleij wrote: >> No matter whether it's a switch or a GPIO regulator it seems we >> are in violent agreement that it should not be controlled by the >> pin control states at least. >> >> Start with making it a GPIO then you can figure out whether >> a GPIO regulator or drivers/extcon/extcon-gpio.c should be >> used. > > Thanks for pointing this out. I wasn't aware of the extcon subsystem. > > Actually, I think it's a little bit more tricky. Hm, yeah extcon is for things like audio jacks on phones that userspace need to detect. drivers/input/keyboard/gpio_keys* is for things that actually input characters to userspace stuff. None of it is applicable here it seems ... > The switch connected to gpio PB22 is used to enable one device or the other: > - PB22 set to high level enables slot0 of mmc0 (connect mmc signals to the > mmc > connector) > - PB22 set to low level enables the dataflash (connect to the SPI0 signals > to the > dataflash device) So this is something like a "jumper" of the old type, configuring the entire system? Something like that: http://www.mignonette-game.com/images/v2/21-arduino-com-jumper.jpg But in this case it is a mechanical switch rather than a jumper? This is not much different from the GPIOs people use to e.g. encode the board type, just that it can change. Do people switch this thing at runtime? > The pinctrl approach has the benefit of providing a transparent way (no > existing > drivers modifications) to enable one device or the other. > > But if you think this is better done (or cleaner) with an extcon or a > regulator device, > I'll try to find a way to do it this way. I'm uncertain. If this is something that changes at runtime, the input from the switch should be read through GPIO and used to select the "default" state of one device and something like "sleep" on the other (I suspect more things than pin control may be affected by that!) If this is a switch that you want to take the simple shortcut of just reading at boot, the approach would still be similar, just less code. So use gpio_get() to read the value, and then select which *entire device* goes active depending on the setting would be the right approach I guess? Yours, Linus Walleij -- 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
