1 What: /sys/class/gpio/ 1 What: /sys/class/gpio/
2 Date: July 2008 2 Date: July 2008
3 KernelVersion: 2.6.27 3 KernelVersion: 2.6.27
4 Contact: Linus Walleij <linusw@kernel.or 4 Contact: Linus Walleij <linusw@kernel.org>
5 Description: 5 Description:
6 6
7 As a Kconfig option, individual GPIO signals 7 As a Kconfig option, individual GPIO signals may be accessed from
8 userspace. GPIOs are only made available to 8 userspace. GPIOs are only made available to userspace by an explicit
9 "export" operation. If a given GPIO is not 9 "export" operation. If a given GPIO is not claimed for use by
10 kernel code, it may be exported by userspace 10 kernel code, it may be exported by userspace (and unexported later).
11 Kernel code may export it for complete or pa 11 Kernel code may export it for complete or partial access.
12 12
13 GPIOs are identified as they are inside the 13 GPIOs are identified as they are inside the kernel, using integers in
14 the range 0..INT_MAX. See Documentation/adm !! 14 the range 0..INT_MAX. See Documentation/gpio.txt for more information.
15 <<
16 :: <<
17 15
18 /sys/class/gpio 16 /sys/class/gpio
19 /export ... asks the kernel to export 17 /export ... asks the kernel to export a GPIO to userspace
20 /unexport ... to return a GPIO to the 18 /unexport ... to return a GPIO to the kernel
21 /gpioN ... for each exported GPIO #N O 19 /gpioN ... for each exported GPIO #N OR
22 /<LINE-NAME> ... for a properly named 20 /<LINE-NAME> ... for a properly named GPIO line
23 /value ... always readable, writes 21 /value ... always readable, writes fail for input GPIOs
24 /direction ... r/w as: in, out (de 22 /direction ... r/w as: in, out (default low); write: high, low
25 /edge ... r/w as: none, falling, r 23 /edge ... r/w as: none, falling, rising, both
26 /gpiochipN ... for each gpiochip; #N i 24 /gpiochipN ... for each gpiochip; #N is its first GPIO
27 /base ... (r/o) same as N 25 /base ... (r/o) same as N
28 /label ... (r/o) descriptive, not 26 /label ... (r/o) descriptive, not necessarily unique
29 /ngpio ... (r/o) number of GPIOs; 27 /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
30 28
31 This ABI is obsoleted by Documentation/ABI/t !! 29 This ABI is deprecated and will be removed after 2020. It is
32 removed after 2020. !! 30 replaced with the GPIO character device.
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