Anti Sullin <anti.sullin@xxxxxxxxxxxxxx> wrote: > Haavard Skinnemoen wrote: > > I don't think the gpio layer is supposed to touch the portmux. David > > has always been very clear about that. But if we somehow manage to get > > the pin configured as a GPIO, we can use the GPIO layer to request a > > pin change interrupt. > > > > It _might_ work even if you don't reconfigure the pin as a GPIO...but > > then I think we'd be relying on undocumented behaviour. > > > I believe that you don't need to reconfigure the pin. The gpio hw does > not require the pin to be multiplexed to any given state, so does not request_irq (correct?). > I did this trick in my [2/3] MCI driver patch I sent to arm-linux-kernel at 18.03.2008 (the > e-mail subject line was wrong, [1/3], though) and I'm using that patch still on my > production devices to avoid some rare but critical SD data corruption (mainline kernel still > screws up the filesystem on SD sometimes). The same should be easily usable on serial port, too. You're right. It works, and it's documented. I don't think it's guaranteed by the GPIO API, but as long as it's guaranteed on AT91 and AVR32, we should be fine. > So in many applications we could not use this. But this might still come handy > in a lot of cases we can poll and find out what caused the data on the serial > port etc. Or on applications, where this loss of data does not matter (like debug > console where the resume is usable even if it does not wake up on the first byte). Yes, as long as you have some sort of timeout/retry mechanism in place, it might be useful. Haavard -- 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
