On Thu, Jan 23, 2014 at 2:16 PM, Jean-Jacques Hiblot <[email protected]> wrote:
> I've been thinking hard on the gpio ownership and I'd like your > opinion on the following assumptions: > > - a gpio used as an interrupt is always a gpio configured as an input. > (corollary : a gpio used for interrupt cannot not be an ouput) That is the assumption made by the core. Until the day someone comes up with a weird usecase... > - a gpio used as an input or interrupt only, could be safely accessed > by multiple users. Multiple consumers is the term we would use. But yes. > - a gpio used as an output should be used as such by only one user. > Still other users should be allowed to read its value. Sounds reasonable. > If those assumptions are true, I believe they can lead to a new > exclusion scheme: > - ouput is mutually exclusive with interrupt but not with input > - only 1 ouput user at a time. Logical conclusion from the above yes. > It would do away with our sharing issue and more (chained interrupt > handlers on gpio interrupt, read/interrupt access through sysfs to a > gpio requested by a driver) > > And I believe that most of the infrastructure is in place to implement this : > - direction flags in gpio_request_one > - gpio_lock_as_irq/gpio_unlock_as_irq So I think what I need to see is a proposed patch, whether it will hit a particular driver or the gpiolib core, but either would probably be interesting. Pls keep linux-gpio and Alexandre on CC for this discussion. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
