| 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 |
| /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) |
| |