On Sun, May 29, 2016 at 9:29 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > On 24/05/16 13:35, Crestez Dan Leonard wrote: >> This might be completely crazy, but wouldn't it be possible to support >> gpio level interrupts purely in software? Just read the GPIO state again >> after the interrupt is unmasked and retrigger. >> >> This seems preferable to implementing per-driver workarounds. Perhaps it >> would even fit in some gpio-irqchip glue. > > That's precisely the question I raised way back when writing the lis3l02dq > driver. Apparently someone once had a go but it never went anywhere... It is maybe possible to do in some cases. What you have to do is to augment the GPIO irqchip driver to read the line status register after handling an IRQ, if level IRQ is desired, and if the line is still high after a rising edge or still low after a falling edge, just call the IRQ handler again. This will not work with threaded interrupt handlers, because that code is in the "hard" path of the interrupt handling code, that gets executed in response to an IRQ signal. What it would take is code to go back into the "hard" irq handler after the thread has run, and take a second lap in checking the line levels. I don't know if that is possible to achieve in Linux, hm :/ Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
