gpio: add userspace ABI for GPIO line information
This adds a GPIO line ABI for getting name, label and a few select flags from the kernel. This hides the kernel internals and only tells userspace what it may need to know: the different in-kernel consumers are masked behind the flag "kernel" and that is all userspace needs to know. However electric characteristics like active low, open drain etc are reflected to userspace, as this is important information. We provide information on all lines on all chips, later on we will likely add a flag for the chardev consumer so we can filter and display only the lines userspace actually uses in e.g. lsgpio, but then we first need an ABI for userspace to grab and use (get/set/select direction) a GPIO line. Sample output from "lsgpio" on ux500: GPIO chip: gpiochip7, "8011e000.gpio", 32 GPIO lines line 0: unnamed unlabeled line 1: unnamed unlabeled (...) line 25: unnamed "SFH7741 Proximity Sensor" [kernel output open-drain] line 26: unnamed unlabeled (...) Tested-by:Michael Welling <mwelling@ieee.org> Signed-off-by:
Linus Walleij <linus.walleij@linaro.org>
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df4878e9