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Diffstat (limited to 'Documentation/ABI/obsolete/sysfs-gpio')
| -rw-r--r-- | Documentation/ABI/obsolete/sysfs-gpio | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Documentation/ABI/obsolete/sysfs-gpio b/Documentation/ABI/obsolete/sysfs-gpio new file mode 100644 index 000000000000..867c1fab20e2 --- /dev/null +++ b/Documentation/ABI/obsolete/sysfs-gpio @@ -0,0 +1,30 @@ +What: /sys/class/gpio/ +Date: July 2008 +KernelVersion: 2.6.27 +Contact: Linus Walleij <linusw@kernel.org> +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) + + This ABI is deprecated and will be removed after 2020. It is + replaced with the GPIO character device. |