pwm: Add sysfs interface

Add a simple sysfs interface to the generic PWM framework.

  /sys/class/pwm/
  `-- pwmchipN/           for each PWM chip
      |-- export          (w/o) ask the kernel to export a PWM channel
      |-- npwm            (r/o) number of PWM channels in this PWM chip
      |-- pwmX/           for each exported PWM channel
      |   |-- duty_cycle  (r/w) duty cycle (in nanoseconds)
      |   |-- enable      (r/w) enable/disable PWM
      |   |-- period      (r/w) period (in nanoseconds)
      |   `-- polarity    (r/w) polarity of PWM (normal/inversed)
      `-- unexport        (w/o) return a PWM channel to the kernel

Based on work by Lars Poeschel.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-pwm b/Documentation/ABI/testing/sysfs-class-pwm
new file mode 100644
index 000000000000..c479d77b67c5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-pwm
@@ -0,0 +1,79 @@
+What:		/sys/class/pwm/
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		The pwm/ class sub-directory belongs to the Generic PWM
+		Framework and provides a sysfs interface for using PWM
+		channels.
+
+What:		/sys/class/pwm/pwmchipN/
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		A /sys/class/pwm/pwmchipN directory is created for each
+		probed PWM controller/chip where N is the base of the
+		PWM chip.
+
+What:		/sys/class/pwm/pwmchipN/npwm
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		The number of PWM channels supported by the PWM chip.
+
+What:		/sys/class/pwm/pwmchipN/export
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Exports a PWM channel from the PWM chip for sysfs control.
+		Value is between 0 and /sys/class/pwm/pwmchipN/npwm - 1.
+
+What:		/sys/class/pwm/pwmchipN/unexport
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Unexports a PWM channel.
+
+What:		/sys/class/pwm/pwmchipN/pwmX
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		A /sys/class/pwm/pwmchipN/pwmX directory is created for
+		each exported PWM channel where X is the exported PWM
+		channel number.
+
+What:		/sys/class/pwm/pwmchipN/pwmX/period
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Sets the PWM signal period in nanoseconds.
+
+What:		/sys/class/pwm/pwmchipN/pwmX/duty_cycle
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Sets the PWM signal duty cycle in nanoseconds.
+
+What:		/sys/class/pwm/pwmchipN/pwmX/polarity
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Sets the output polarity of the PWM signal to "normal" or
+		"inversed".
+
+What:		/sys/class/pwm/pwmchipN/pwmX/enable
+Date:		May 2013
+KernelVersion:	3.11
+Contact:	H Hartley Sweeten <hsweeten@visionengravers.com>
+Description:
+		Enable/disable the PWM signal.
+		0 is disabled
+		1 is enabled