114 lines
4.6 KiB
Groff
114 lines
4.6 KiB
Groff
.\" Copyright (c) 2018 Emmanuel Vadot <manu@freebsd.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 21, 2019
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.Dt PWMBUS 9
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.Os
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.Sh NAME
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.Nm pwmbus ,
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.Nm PWMBUS_CHANNEL_CONFIG ,
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.Nm PWMBUS_CHANNEL_COUNT ,
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.Nm PWMBUS_CHANNEL_ENABLE ,
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.Nm PWMBUS_CHANNEL_GET_CONFIG ,
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.Nm PWMBUS_CHANNEL_GET_FLAGS ,
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.Nm PWMBUS_CHANNEL_IS_ENABLED ,
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.Nm PWMBUS_CHANNEL_SET_FLAGS ,
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.Nm PWMBUS_GET_BUS
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.Nd PWMBUS methods
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.Sh SYNOPSIS
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.Cd "device pwm"
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.In "pwmbus_if.h"
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.Ft int
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.Fn PWMBUS_CHANNEL_CONFIG "device_t bus" "int channel" "uint64_t period" "uint64_t duty"
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.Ft int
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.Fn PWMBUS_CHANNEL_COUNT "device_t bus" "int channel" "int *nchannel"
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.Ft int
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.Fn PWMBUS_CHANNEL_ENABLE "device_t bus" "int channel" "bool enable"
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.Ft int
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.Fn PWMBUS_CHANNEL_GET_CONFIG "device_t bus" "int channel" "uint64_t *period" "uint64_t *duty"
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.Ft int
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.Fn PWMBUS_CHANNEL_GET_FLAGS "device_t bus" "int channel" "uint32_t *flags"
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.Ft int
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.Fn PWMBUS_CHANNEL_IS_ENABLED "device_t bus" "int channel" "bool *enabled"
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.Ft int
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.Fn PWMBUS_CHANNEL_SET_FLAGS "device_t bus" "int channel" "uint32_t flags"
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.Sh DESCRIPTION
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The PWMBUS (Pulse-Width Modulation) interface allows a device driver to
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register to a global bus so other devices in the kernel can use them in a
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generic way.
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.Pp
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For all
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.Nm
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methods, the
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.Va period
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argument is the duration in nanoseconds of one complete on-off cycle, and the
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.Va duty
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argument is the duration in nanoseconds of the on portion of that cycle.
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.Pp
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Some PWM hardware is organized as a single controller with multiple channels.
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Channel numbers count up from zero.
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When multiple channels are present, they sometimes share a common clock or
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other resources.
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In such cases, changing the period or duty cycle of any one channel may affect
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other channels within the hardware which share the same resources.
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Consult the documentation for the underlying PWM hardware device driver for
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details on channels that share resources.
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.Sh INTERFACE
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.Bl -tag -width indent
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.It Fn PWMBUS_CHANNEL_CONFIG "device_t bus" "int channel" "uint64_t period" "uint64_t duty"
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Configure the period and duty (in nanoseconds) in the PWM controller on the bus
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for the specified channel.
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Returns 0 on success or
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.Er EINVAL
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if the values are not supported by the controller or
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.Er EBUSY
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if the PWMBUS controller is in use and does not support changing the value on
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the fly.
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.It Fn PWMBUS_CHANNEL_COUNT "device_t bus" "int *nchannel"
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Get the number of channels supported by the controller.
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.It Fn PWMBUS_CHANNEL_ENABLE "device_t bus" "int channel" "bool enable"
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Enable the PWM channel.
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.It Fn PWMBUS_CHANNEL_GET_CONFIG "device_t bus" "int channel" "uint64_t *period" "uint64_t *duty"
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Get the current configuration of the period and duty for the specified channel.
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.It Fn PWMBUS_CHANNEL_GET_FLAGS "device_t bus" "int channel" "uint32_t *flags"
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Get the current flags for the channel.
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If the driver or controller
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does not support this, a default method returns a flags value of zero.
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.It Fn PWMBUS_CHANNEL_IS_ENABLED "device_t bus" "int channel" "bool *enable"
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Test whether the PWM channel is enabled.
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.It Fn PWMBUS_CHANNEL_SET_FLAGS "device_t bus" "int channel" "uint32_t flags"
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Set the flags of the channel (such as inverted polarity).
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If the driver or controller does not support this a do-nothing default method
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is used.
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.El
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.Sh HISTORY
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The
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.Nm pwmbus
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interface first appear in
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.Fx 13.0 .
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The
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.Nm pwmbus
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interface and manual page was written by
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.An Emmanuel Vadot Aq Mt manu@FreeBSD.org .
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