From: David Brownell <dbrownell@users.sourceforge.net>
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>
---
For 2.6.27 ... let's make Greg happy. :)
Documentation/ABI/testing/sysfs-gpio | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ b/Documentation/ABI/testing/sysfs-gpio 2008-07-25 12:38:50.000000000 -0700
@@ -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)
+
--
