diff options
| author | David Brownell <dbrownell@users.sourceforge.net> | 2008-09-13 02:33:20 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-09-13 14:41:52 -0700 |
| commit | 9f986a8cdf94a5855201cf67db6ffdf926bc4cd9 (patch) | |
| tree | 7c74f8727f2baa389f2305b43a9e3f21bb650c77 | |
| parent | 5bead2a0680687b9576d57c177988e8aa082b922 (diff) | |
Documentation/ABI: /sys/class/gpio
Provide summary ABI docs about the /sys/class/gpio files.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | Documentation/ABI/testing/sysfs-gpio | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/testing/sysfs-gpio new file mode 100644 index 00000000000..8aab8092ad3 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-gpio @@ -0,0 +1,26 @@ +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 + /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) + |