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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
+
+What: /sys/class/pwm/pwmchipN/pwmX/capture
+Date: June 2016
+KernelVersion: 4.8
+Contact: Lee Jones <lee.jones@linaro.org>
+Description:
+ Capture information about a PWM signal. The output format is a
+ pair unsigned integers (period and duty cycle), separated by a
+ single space.