For a long period value and the duty specified as a percentage,
there could be an overflow.
Using unsigned integers aligns the code with struct pwm_state and allows
to safely use periods up to 4 seconds where supported by drivers.
MFC after: 2 weeks
can be combined with configuring the period and duty cycle (the same ioctl
sets all 3 values at once, so there's no reason to require the user to run
the program twice to get all 3 things set).
The driver now names its cdev nodes pwmcX.Y where X is unit number and
Y is the channel within that unit. Change the default device name from
pwmc0 to pwmc0.0. The driver now puts cdev files and label aliases in
the /dev/pwm directory, so allow the user to provide unqualified names
with -f and automatically prepend the /dev/pwm part for them.
Update the examples in the manpage to show the new device name format
and location within /dev/pwm.
ioctl definitions and related datatypes that allow userland control of pwm
hardware via the pwmc device. The new name and location better reflects its
assocation with a single device driver.
The pwm subsystem consist of API for PWM controllers, pwmbus to register them
and a pwm(8) utility to talk to them from userland.
Reviewed by: oshgobo (capsicum), bcr (manpage), 0mp (manpage)
Differential Revision: https://reviews.freebsd.org/D17938
