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authorDaniel Glöckner <dg@emlix.com>2009-09-22 16:46:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 07:39:48 -0700
commitff77c352ae17768c61cfc36357f0a3904552f11c (patch)
tree195c102f75445654e87453cbce284b2f658d13a8 /Documentation/ABI/testing
parentd120c17faeb391f5b4b99af8b1e190619934ecdd (diff)
gpiolib: allow poll() on value
Many gpio chips allow to generate interrupts when the value of a pin changes. This patch gives usermode application the opportunity to make use of this feature by calling poll(2) on the /sys/class/gpio/gpioN/value sysfs file. The edge to trigger can be set in the edge file in the same directory. Possible values are "none", "rising", "falling", and "both". Using level triggers is not possible with current sysfs since nothing changes the GPIO value (and the IRQ keeps triggering). Edge triggering will "just work". Note that if there was an event between read() and poll(), the poll() returns immediately. Also note that this version only supports true GPIO interrupts. Some later patch might be able to synthesize this behavior by timer-driven polling; some systems seem to need that. [dbrownell@users.sourceforge.net: align ids to 16 bit ids; whitespace] Signed-off-by: Daniel Glöckner <dg@emlix.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/ABI/testing')
-rw-r--r--Documentation/ABI/testing/sysfs-gpio1
1 files changed, 1 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/testing/sysfs-gpio
index 8aab8092ad3..80f4c94c7be 100644
--- a/Documentation/ABI/testing/sysfs-gpio
+++ b/Documentation/ABI/testing/sysfs-gpio
@@ -19,6 +19,7 @@ Description:
/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