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Slightly improve usb(4)

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- Mention USB 3.0
- Update links
- Fix `mandoc -T lint` warnings

Reviewed by:	bcr, hselasky
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D26349
This commit is contained in:
Li-Wen Hsu 2020-09-07 07:44:14 +00:00
parent 1668d773a4
commit eddaeb2095
1 changed files with 14 additions and 26 deletions
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40
share/man/man4/usb.4
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@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd April 24, 2018
.Dd September 7, 2020
.Dt USB 4
.Os
.Sh NAME
@ -52,8 +52,7 @@ for more information.
.Sh DESCRIPTION
.Fx
provides machine-independent bus support and drivers for
.Tn USB
devices in host and device side mode.
USB devices in host and device side mode.
.Pp
The
.Nm
@ -67,32 +66,25 @@ driver has three layers:
The controller attaches to a physical bus
like
.Xr pci 4 .
The
.Tn USB
bus attaches to the controller, and the root hub attaches
The USB bus attaches to the controller, and the root hub attaches
to the controller.
Any devices attached to the bus will attach to the root hub
or another hub attached to the
.Tn USB
bus.
or another hub attached to the USB bus.
.Pp
The
.Nm uhub
device will always be present as it is needed for the root hub.
.Sh INTRODUCTION TO USB
The
.Tn USB
is a system where external devices can be connected to a PC.
The USB is a system where external devices can be connected to a PC.
The most common USB speeds are:
.Bl -tag -width 6n -offset indent
.It Low Speed (1.5MBit/sec)
.It Full Speed (12MBit/sec)
.It High Speed (480MBit/sec)
.It Low Speed (1.5 MBit/sec)
.It Full Speed (12 MBit/sec)
.It High Speed (480 MBit/sec)
.It SuperSpeed (5 GBit/sec)
.El
.Pp
Each
.Tn USB
has a USB controller that is the master of the bus.
Each USB has a USB controller that is the master of the bus.
The physical communication is simplex which means the host controller only
communicates with one USB device at a time.
.Pp
@ -122,9 +114,7 @@ A device may operate in different configurations.
Depending on the configuration, the device may present different sets of
endpoints and interfaces.
.Pp
The bus enumeration of the
.Tn USB
bus proceeds in several steps:
The bus enumeration of the USB bus proceeds in several steps:
.Bl -enum
.It
Any interface specific driver can attach to the device.
@ -144,11 +134,9 @@ debug message verbosity.
Default is 0.
.El
.Sh SEE ALSO
The
.Tn USB
specifications can be found at:
The USB specifications can be found at:
.Pp
.D1 Pa http://www.usb.org/developers/docs/
.D1 Pa https://www.usb.org/documents
.Pp
.Xr libusb 3 ,
.Xr aue 4 ,
@ -178,7 +166,7 @@ specifications can be found at:
.Sh STANDARDS
The
.Nm
module complies with the USB 2.0 standard.
module complies with the USB 3.0 standard.
.Sh HISTORY
The
.Nm