spent an agonizing last 24 hours or so on debugging why my device tree modification wasn't even being added to the sysfs slots directory, let alone work as intended.

it seems there's a hidden, and arbitrary, length for either the "part-number" or for the labels, and it's less than 21: "bb_gpio_test" works, and "bbb_switched_led_test" does not.

only by fiddling with it was I able to determine this. there was no error message I could find anywhere which gave any clue why echoing the "part-number" into $SLOTS was returning a nonzero exit code.

now I've still got to figure out how to take the BeagleBone Black's switch S2 and LED USR1 away from whatever driver now "owns" them. that's my next step.

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last updated 2017-07-12 10:10:49. served from tektonic