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.
Bug
200028381
Change-Id: I0c9c6ad2ca7173e6fc3fbe1d3cd3963cde00539a
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>
Signed-off-by: Bibek Basu <bbasu@nvidia.com>
(cherry picked from commit
76abbdde2d95a3807d0dc6bf9f84d03d0dbd4f3d)
Reviewed-on: http://git-master/r/455068
(cherry picked from commit
b1824bc0325f84ea04dab7d6d4f7c887c80b1982)
Reviewed-on: http://git-master/r/488690
GVS: Gerrit_Virtual_Submit
Reviewed-by: Winnie Hsu <whsu@nvidia.com>
Tested-by: Winnie Hsu <whsu@nvidia.com>