On Mon, Aug 22, 2016 at 5:45 PM, One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx> wrote: > and if I look at the usermode crapfest on a lot of Android systems it > looks similar but with the notion of things like being able to describe > > - Use GPIO mode sleeping and assume first char is X to save power It's really nasty hardware design, or a software hack to solve a hardware problem: what should have been done is of course create a UART with an asynchronous low-power mode that can recieve a character and wake up the system at any time, handing over the wakeup character(s) to the driver. That is obviously the usecase they were designing for. But yeah, I guess we have to contain hacks like that. > - Power up, wait n ms, write, read, wait n ms, power down (which > has to be driven at the ldisc/user level as only the ldisc > understands transactions, or via ioctls (right now Android user > space tends to do hardcoded writes to /sys.. gpio to drive power This kind of abominational abuse of the GPIO sysfs ABI is partly why I've obsoleted it. The right abstraction is the fixed regulator with a GPIO line obviously, then some sequencing along the lines of what you can find in drivers/mmc/core/pwrseq* Unfortunately that sysfs ABI crept in during a window of time when GPIO was unmaintained and I am trying my best to contain and improve the situation. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
