1What:		/sys/class/gpio/
2Date:		July 2008
3KernelVersion:	2.6.27
4Contact:	David Brownell <dbrownell@users.sourceforge.net>
5Description:
6
7  As a Kconfig option, individual GPIO signals may be accessed from
8  userspace.  GPIOs are only made available to userspace by an explicit
9  "export" operation.  If a given GPIO is not claimed for use by
10  kernel code, it may be exported by userspace (and unexported later).
11  Kernel code may export it for complete or partial access.
12
13  GPIOs are identified as they are inside the kernel, using integers in
14  the range 0..INT_MAX.  See Documentation/gpio.txt for more information.
15
16    /sys/class/gpio
17	/export ... asks the kernel to export a GPIO to userspace
18	/unexport ... to return a GPIO to the kernel
19	/gpioN ... for each exported GPIO #N OR
20	/<LINE-NAME> ... for a properly named GPIO line
21	    /value ... always readable, writes fail for input GPIOs
22	    /direction ... r/w as: in, out (default low); write: high, low
23	    /edge ... r/w as: none, falling, rising, both
24	/gpiochipN ... for each gpiochip; #N is its first GPIO
25	    /base ... (r/o) same as N
26	    /label ... (r/o) descriptive, not necessarily unique
27	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
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