MFC r258044, r258679, r263990

Adds gpioiic.4 and gpioled.4 man pages.  Moves some of the information that
was previously available on gpio.4 to their respectives pages.  Add the
cross references on gpioctl.8.

Add gpiobus(4) as a link to gpio(4).

1 files changed, 15 insertions, 48 deletions

diff --git a/share/man/man4/gpio.4 b/share/man/man4/gpio.4
index 614a722..f0bd8a3 100644
--- a/share/man/man4/gpio.4
+++ b/share/man/man4/gpio.4
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 13, 2013
+.Dd November 5, 2013
 .Dt GPIO 4
 .Os
 .Sh NAME
@@ -34,10 +34,9 @@
 To compile these devices into your kernel and use the device hints, place the
 following lines in your kernel configuration file:
 .Bd -ragged -offset indent
-.Cd "device gpiobus"
-.Cd "device gpioiic"
 .Cd "device gpio"
 .Cd "device gpioc"
+.Cd "device gpioiic"
 .Cd "device gpioled"
 .Ed
 .Pp
@@ -76,8 +75,9 @@ architecure include:
 .Sh DESCRIPTION
 The
 .Em gpiobus
-system provides a simple interface to the bit banging style GPIO bus
-found on embedded architectures.
+system provides a simple interface to the GPIO pins that are usually
+available on embedded architectures and can provide bit banging style
+devices to the system.
 .Pp
 The acronym
 .Li GPIO
@@ -88,36 +88,20 @@ The BUS physically consists of multiple pins that can be configured
 for input/output, IRQ delivery, SDA/SCL
 .Em iicbus
 use, etc.
-On most embedded architechtures (mips/arm), discovery of the bus and
+.Pp
+On some embedded architechtures (like MIPS), discovery of the bus and
 configuration of the pins is done via
 .Xr device.hints 5
 in the platform's kernel
 .Xr config 5
 file.
 .Pp
-Assignment of
-.Xr gpioiic 4
-bus variables is done via:
-.Bl -tag -width ".Va hint.gpioiic.%d.atXXX"
-.It Va hint.gpioiic.%d.at
-Normally just gpiobus0.
-.It Va hint.gpioiic.%d.pins
-This is a bitmask of the pins on the gpio board that are to be used for
-SCLOCK and SDATA from the IIC bus.
-To configure pin 0 and 7, use the bitmask of
-10000001 and convert it to a hexadecimal value of 0x0081.
-Should only ever have two bits set in mask.
-.It Va hint.gpioiic.%d.scl
-Indicates which bit in the
-.Va hint.gpioiic.%d.pins
-should be used as the SCLOCK
-source.
-.It Va hint.gpioiic.%d.sda
-Indicates which bit in the
-.Va hint.gpioiic.%d.pins
-should be used as the SDATA
-source.
-.El
+On some others (like ARM), where
+.Xr FDT 4
+is used to describe the device tree, the bus discovery is done via the DTS
+passed to the kernel, being either statically compiled in, or by a variety
+of ways where the boot loader (or Open Firmware enabled system) passes the
+DTS blob to kernel at boot.
 .Pp
 The following are only provided by the
 .Cd ar71xx_gpio
@@ -141,28 +125,11 @@ This is mainly used to set/clear functions that we need when they are setup or
 not setup by uBoot.
 .El
 .Pp
-These values are configureable from the
-.Xr gpioled 4
-interface and help create
-.Xr led 4
-compatible devices in
-.Pa /dev/led/<name> .
-.Bl -tag -width ".Va hint.gpioiic.%d.atXXX"
-.It Va hint.gpioled.%d.at
-Normally assigned to gpiobus0.
-.It Va hint.gpioled.%d.name
-Arbitrary name of device in
-.Pa /dev/led/
-to create for
-.Xr led 4
-interfaces.
-.It Va hint.gpioled.%d.pins
-Which pin on the GPIO interface to map to this instance.
-.El
-.Pp
 Simply put, each pin of the GPIO interface is connected to an input/output
 of some device in a system.
 .Sh SEE ALSO
+.Xr gpioiic 4 ,
+.Xr gpioled 4 ,
 .Xr iicbus 4 ,
 .Xr gpioctl 8
 .Sh HISTORY