svn commit: r349165 - head/usr.sbin/pwm

[Ian Lepore]

Author: ian
Date: Tue Jun 18 00:17:10 2019
New Revision: 349165
URL: https://svnweb.freebsd.org/changeset/base/349165

Log:
  Explain the relationship between PWM hardware channels being controlled and
  pwmc(4) device filenames.  Also, use uppercase PWM when the term is being
  used as an acronym, and expand the acronym where it's first used.

Modified:
  head/usr.sbin/pwm/pwm.8

Modified: head/usr.sbin/pwm/pwm.8
==============================================================================
--- head/usr.sbin/pwm/pwm.8	Tue Jun 18 00:11:00 2019	(r349164)
+++ head/usr.sbin/pwm/pwm.8	Tue Jun 18 00:17:10 2019	(r349165)
@@ -27,7 +27,7 @@
 .Os
 .Sh NAME
 .Nm pwm
-.Nd configure pwm controller
+.Nd configure PWM (Pulse Width Modulation) hardware
 .Sh SYNOPSIS
 .Nm
 .Op Fl f Ar device
@@ -47,9 +47,26 @@
 .Sh DESCRIPTION
 The
 .Nm
-utility can be used to configure pwm controllers.
+utility can be used to configure pwm hardware.
+.Nm
+uses a
+.Xr pwmc 4
+device to communicate with the hardware.
+Some PWM hardware supports multiple output channels within a single
+controller block; each
+.Xr pwmc 4
+instance controls a single PWM channel.
 .Pp
-The options are as follow:
+.Xr pwmc 4
+devices are named
+.Pa /dev/pwm/pwmcX.Y ,
+where
+.Va X
+is the controller unit number and
+.Va Y
+is the channel number within that unit.
+.Pp
+The options are as follows:
 .Bl -tag -width "-f device"
 .It Fl f Ar device
 Device to operate on.
@@ -60,15 +77,15 @@ If an unqualified name is provided,
 .Pa /dev/pwm
 is automatically prepended.
 .It Fl E
-Enable the pwm channel.
+Enable the PWM channel.
 .It Fl D
-Disable the pwm channel.
+Disable the PWM channel.
 .It Fl C
-Show the configuration of the pwm channel.
+Show the configuration of the PWM channel.
 .It Fl p Ar period
-Configure the period (in nanoseconds) of the pwm channel
+Configure the period (in nanoseconds) of the PWM channel
 .It Fl d Ar duty
-Configure the duty (in nanoseconds or percentage) of the pwm channel.
+Configure the duty (in nanoseconds or percentage) of the PWM channel.
 Duty is the portion of the
 .Ar period
 during which the signal is asserted.
@@ -76,7 +93,7 @@ during which the signal is asserted.
 .Sh EXAMPLES
 .Bl -bullet
 .It
-Show the configuration of the pwm channel:
+Show the configuration of the PWM channel:
 .Bd -literal
 pwm -f /dev/pwm/pwmc0.1 -C
 .Ed