PWMBUS(9)              FreeBSD Kernel Developer's Manual             PWMBUS(9)

NAME
     pwmbus, PWMBUS_CHANNEL_CONFIG, PWMBUS_CHANNEL_COUNT,
     PWMBUS_CHANNEL_ENABLE, PWMBUS_CHANNEL_GET_CONFIG,
     PWMBUS_CHANNEL_GET_FLAGS, PWMBUS_CHANNEL_IS_ENABLED,
     PWMBUS_CHANNEL_SET_FLAGS, PWMBUS_GET_BUS - PWMBUS methods

SYNOPSIS
     device pwm
     #include <pwmbus_if.h>

     int
     PWMBUS_CHANNEL_CONFIG(device_t bus, u_int channel, u_int period,
         u_int duty);

     int
     PWMBUS_CHANNEL_COUNT(device_t bus, u_int *nchannel);

     int
     PWMBUS_CHANNEL_ENABLE(device_t bus, u_int channel, bool enable);

     int
     PWMBUS_CHANNEL_GET_CONFIG(device_t bus, u_int channel, u_int *period,
         u_int *duty);

     int
     PWMBUS_CHANNEL_GET_FLAGS(device_t bus, u_int channel, uint32_t *flags);

     int
     PWMBUS_CHANNEL_IS_ENABLED(device_t bus, u_int channel, bool *enabled);

     int
     PWMBUS_CHANNEL_SET_FLAGS(device_t bus, u_int channel, uint32_t flags);

DESCRIPTION
     The PWMBUS (Pulse-Width Modulation) interface allows a device driver to
     register to a global bus so other devices in the kernel can use them in a
     generic way.

     For all pwmbus methods, the period argument is the duration in
     nanoseconds of one complete on-off cycle, and the duty argument is the
     duration in nanoseconds of the on portion of that cycle.

     Some PWM hardware is organized as a single controller with multiple
     channels.  Channel numbers count up from zero.  When multiple channels
     are present, they sometimes share a common clock or other resources.  In
     such cases, changing the period or duty cycle of any one channel may
     affect other channels within the hardware which share the same resources.
     Consult the documentation for the underlying PWM hardware device driver
     for details on channels that share resources.

INTERFACE
     PWMBUS_CHANNEL_CONFIG(device_t bus, u_int channel, u_int period, u_int
             duty)
             Configure the period and duty (in nanoseconds) in the PWM
             controller on the bus for the specified channel.  Returns 0 on
             success or EINVAL if the values are not supported by the
             controller or EBUSY if the PWMBUS controller is in use and does
             not support changing the value on the fly.

     PWMBUS_CHANNEL_COUNT(device_t bus, u_int *nchannel)
             Get the number of channels supported by the controller.

     PWMBUS_CHANNEL_ENABLE(device_t bus, u_int channel, bool enable)
             Enable the PWM channel.

     PWMBUS_CHANNEL_GET_CONFIG(device_t bus, u_int channel, u_int *period,
             u_int *duty)
             Get the current configuration of the period and duty for the
             specified channel.

     PWMBUS_CHANNEL_GET_FLAGS(device_t bus, u_int channel, uint32_t *flags)
             Get the current flags for the channel.  If the driver or
             controller does not support this, a default method returns a
             flags value of zero.

     PWMBUS_CHANNEL_IS_ENABLED(device_t bus, u_int channel, bool *enable)
             Test whether the PWM channel is enabled.

     PWMBUS_CHANNEL_SET_FLAGS(device_t bus, u_int channel, uint32_t flags)
             Set the flags of the channel (such as inverted polarity).  If the
             driver or controller does not support this a do-nothing default
             method is used.

HISTORY
     The pwmbus interface first appear in FreeBSD 13.0.  The pwmbus interface
     and manual page was written by Emmanuel Vadot <manu@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6          March 9, 2021         FreeBSD 13.1-RELEASE-p6