Hi, I have a question regarding user-space gpio support with sysfs.
Documentation/gpio/sysfs.txt states > GPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42) > and have the following read/write attributes: > > /sys/class/gpio/gpioN/ > > "direction" ... reads as either "in" or "out". This value may > normally be written. ... > > Note that this attribute *will not exist* if the kernel > doesn't support changing the direction of a GPIO, or > it was exported by kernel code that didn't explicitly > allow userspace to reconfigure this GPIO's direction. Imagine for example a generic user-space tool which enumerates all available GPIOs to the user and sorts by input and output GPIOs. How would such a tool classify an exported GPIO when kernel doesn't export the 'direction' file via sysfs? Or in other words: how can userspace detect the state (in vs. out) of a GPIO when 'direction' is not exported? I propose to change the API that direction is always exported, but is only readable when hardware doesn't support changing the direction and/or kernel code wants to prohibit this. Best regards, Michael -- 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
