On Sun, Dec 2, 2018, 8:42 PM Ken Shirriff <[email protected] wrote:
> /sys/class/gpio/export will unexport a pin if accessed twice. Is this a > bug? > > $ echo 13 > /sys/class/gpio/export > $ ls /sys/class/gpio/gpio13 > active_low device direction edge label power subsystem uevent value > $ echo 13 > /sys/class/gpio/export > -bash: echo: write error: Operation not permitted > $ ls /sys/class/gpio/gpio13 > ls: cannot access '/sys/class/gpio/gpio13': No such file or directory > > Expected behavior: gpio13 should still be there after the second export. > Observed behavior: gpio13 disappears after the second export. > > This is with the latest Debian kernel (4.14.71-ti-r80). > > Is there a recommended way to export a gpio pin if it may already exist? I > want to write a script to set up the pins. I could check if each pin > already exists, but that's a recipe for race conditions as well as being > inconvenient. > Don't use that interface... https://blog.adafruit.com/2018/12/02/update-new-gpio-interface-for-linux-user-space-gpio-character-device-api-and-libgpiod-linuxpiter/ Regards, -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAOCHtYg3E_Dm29%2B-4TMbWFxXEtjWQE9vk0ZHVc2e_53QQJ6_Dw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
