| David Brownell | 9f986a8 | 2008-09-13 02:33:20 -0700 | [diff] [blame] | 1 | What: /sys/class/gpio/ |
| 2 | Date: July 2008 |
| 3 | KernelVersion: 2.6.27 |
| 4 | Contact: David Brownell <dbrownell@users.sourceforge.net> |
| 5 | Description: |
| 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 |
| 20 | /value ... always readable, writes fail for input GPIOs |
| 21 | /direction ... r/w as: in, out (default low); write: high, low |
| 22 | /gpiochipN ... for each gpiochip; #N is its first GPIO |
| 23 | /base ... (r/o) same as N |
| 24 | /label ... (r/o) descriptive, not necessarily unique |
| 25 | /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1) |
| 26 | |