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