Re: [avrdude-dev] [bug #44218] linuxgpio not working with raspberryPi 2. "Can't open gpioX/direction" : Permission denied. Fixed by little delay

[Richard Ryniker]

Problem in Raspbian, discussed in:

  https://github.com/raspberrypi/linux/issues/553

Does not occur in Pidora.  Raspbian decided to extend the export
operation to user space but the implementation is ugly - the write to
/sys/class/gpio/export completes before the user-space logic modifies the
created files, which can disrupt use of those files.

"Wait a bit" can help, but is unsatisfactory because there is no reliable
definition of how long "a bit" must be to be effective.  The write to
/sys/class/gpio/export should block until the user-space operation is
complete.