1What:		/sys/class/gpio/
2Date:		July 2008
3KernelVersion:	2.6.27
4Contact:	Linus Walleij <linusw@kernel.org>
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/admin-guide/gpio for more information.
15
16  ::
17
18    /sys/class/gpio
19	/export ... asks the kernel to export a GPIO to userspace
20	/unexport ... to return a GPIO to the kernel
21	/gpioN ... for each exported GPIO #N OR
22	/<LINE-NAME> ... for a properly named GPIO line
23	    /value ... always readable, writes fail for input GPIOs
24	    /direction ... r/w as: in, out (default low); write: high, low
25	    /edge ... r/w as: none, falling, rising, both
26	/gpiochipN ... for each gpiochip; #N is its first GPIO
27	    /base ... (r/o) same as N
28	    /label ... (r/o) descriptive, not necessarily unique
29	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
30
31  This ABI is deprecated and will be removed after 2020. It is
32  replaced with the GPIO character device.
33