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linux-yocto/Documentation/ABI/testing/sysfs-class-pwm
H Hartley Sweeten 76abbdde2d 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>
2013-06-21 11:32:51 +02:00

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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