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, int channel, uint64_t period, uint64_t duty);

     int
     PWMBUS_CHANNEL_COUNT(device_t bus, int channel, int *nchannel);

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

     int
     PWMBUS_CHANNEL_GET_CONFIG(device_t bus, int channel, uint64_t *period, uint64_t *duty);

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

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

     int
     PWMBUS_CHANNEL_SET_FLAGS(device_t bus, 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, int channel, uint64_t period, uint64_t 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, int *nchannel)
             Get the number of channels supported by the controller.

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

     PWMBUS_CHANNEL_GET_CONFIG(device_t bus, int channel, uint64_t *period, uint64_t *duty)
             Get the current configuration of the period and duty for the specified channel.

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

     PWMBUS_CHANNEL_SET_FLAGS(device_t bus, 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>.