forked from Minki/linux
77a775b7cc
commit 926b663ce8
"gpiolib: allow GPIOs to be named" added the ability to
name GPIO lines by an array of names stored in the GPIO
chip. This was in 2009 and has been an ABI since. Let's
document it properly.
Cc: Daniel Silverstone <dsilvers@digital-scurf.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Cc: Johan Hovold <johan@kernel.org>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
29 lines
1.2 KiB
Plaintext
29 lines
1.2 KiB
Plaintext
What: /sys/class/gpio/
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Date: July 2008
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KernelVersion: 2.6.27
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Contact: David Brownell <dbrownell@users.sourceforge.net>
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Description:
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As a Kconfig option, individual GPIO signals may be accessed from
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userspace. GPIOs are only made available to userspace by an explicit
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"export" operation. If a given GPIO is not claimed for use by
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kernel code, it may be exported by userspace (and unexported later).
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Kernel code may export it for complete or partial access.
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GPIOs are identified as they are inside the kernel, using integers in
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the range 0..INT_MAX. See Documentation/gpio.txt for more information.
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/sys/class/gpio
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/export ... asks the kernel to export a GPIO to userspace
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/unexport ... to return a GPIO to the kernel
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/gpioN ... for each exported GPIO #N OR
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/<LINE-NAME> ... for a properly named GPIO line
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/value ... always readable, writes fail for input GPIOs
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/direction ... r/w as: in, out (default low); write: high, low
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/edge ... r/w as: none, falling, rising, both
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/gpiochipN ... for each gpiochip; #N is its first GPIO
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/base ... (r/o) same as N
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/label ... (r/o) descriptive, not necessarily unique
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/ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
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