#!/bin/sh

# udev helper script for setting PWM output device permissions and
# creating and removing the /dev/pwm-X:Y symlink

# Copyright (C)2017-2023, Philip Munts dba Munts Technologies.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
#   this list of conditions and the following disclaimer.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

if [ -z "${DEVPATH}" ]; then
  exit 0
fi

SetPerms()
{
  chown root:plugdev $1
  chmod $2 $1
}

DEVNAME=`basename ${DEVPATH}`
REGEXCHIPMATCH="^pwmchip[0-9]+$"
REGEXCHIPSUBST="pwmchip"

# Handle PWM chip events

echo ${DEVNAME} | egrep "${REGEXCHIPMATCH}"
if [ $? -eq 0 ]; then
  if [ "${ACTION}" = "add" ]; then
    SetPerms /sys${DEVPATH}          0750
    SetPerms /sys${DEVPATH}/export   0220
    SetPerms /sys${DEVPATH}/npwm     0440
    SetPerms /sys${DEVPATH}/unexport 0220
    ln -s -f /sys${DEVPATH} /dev/${DEVNAME}
    exit 0
  fi

  if [ "${ACTION}" = "remove" ]; then
    rm -f /dev/${DEVNAME}
    exit 0
  fi

# Handle PWM chip change events (kernel 4.19)

  if [ "${ACTION}" = "change" ]; then
    if [ -n "${EXPORT}" ]; then
      CHIP=`echo ${DEVNAME} | sed -r "s/${REGEXCHIPSUBST}//g"`
      CHAN=`echo ${EXPORT}  | sed -r "s/pwm//g"`
      CHANPATH=/sys${DEVPATH}/${EXPORT}
      LINKNAME=pwm-${CHIP}:${CHAN}

      SetPerms ${CHANPATH}            0750
      SetPerms ${CHANPATH}/capture    0440
      SetPerms ${CHANPATH}/duty_cycle 0660
      SetPerms ${CHANPATH}/enable     0660
      SetPerms ${CHANPATH}/period     0660
      SetPerms ${CHANPATH}/polarity   0660

      ln -s -f ${CHANPATH} /dev/${LINKNAME}
      exit 0
    fi

    if [ -n "${UNEXPORT}" ]; then
      CHIP=`echo ${DEVNAME}  | sed -r "s/${REGEXCHIPSUBST}//g"`
      CHAN=`echo ${UNEXPORT} | sed -r "s/pwm//g"`
      LINKNAME=pwm-${CHIP}:${CHAN}

      rm -f /dev/pwm-${CHIP}:${CHAN}
      exit 0
    fi
  fi

  exit 0
fi

# Handle PWM channel events (kernel 4.14)

REGEXCHANMATCH="^(pwm-[0-9]+:[0-9]+)|(pwm[0-9]+)$"
REGEXCHANSUBST="(pwm-[0-9]+:)|(pwm)"

echo ${DEVNAME} | egrep "${REGEXCHANMATCH}"
if [ $? -eq 0 ]; then
  PARENTPATH=`dirname ${DEVPATH}`
  PARENTNAME=`basename ${PARENTPATH}`

  CHIP=`echo ${PARENTNAME} | sed -r "s/${REGEXCHIPSUBST}//g"`
  CHAN=`echo ${DEVNAME}    | sed -r "s/${REGEXCHANSUBST}//g"`

  if [ "${ACTION}" = "add" ]; then
    SetPerms /sys${DEVPATH}            0750
    SetPerms /sys${DEVPATH}/capture    0440
    SetPerms /sys${DEVPATH}/duty_cycle 0660
    SetPerms /sys${DEVPATH}/enable     0660
    SetPerms /sys${DEVPATH}/period     0660
    SetPerms /sys${DEVPATH}/polarity   0660

    ln -s -f /sys${DEVPATH} /dev/pwm-${CHIP}:${CHAN}
    exit 0
  fi

  if [ "${ACTION}" = "remove" ]; then
    rm -f /dev/pwm-${CHIP}:${CHAN}
    exit 0
  fi

  exit 0
fi