qemu-options.hx: Improve documentation of chardev multiplexing mode

The current documentation of chardev mux=on is rather brief and opaque;
expand it to hopefully be a bit more helpful.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <1455643738-6068-1-git-send-email-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Maydell 2016-02-16 17:28:58 +00:00 committed by Paolo Bonzini
parent dd5e38b19d
commit a40db1b36b
2 changed files with 63 additions and 12 deletions

View file

@ -158,7 +158,8 @@ TODO (no longer available)
* pcsys_introduction:: Introduction
* pcsys_quickstart:: Quick Start
* sec_invocation:: Invocation
* pcsys_keys:: Keys
* pcsys_keys:: Keys in the graphical frontends
* mux_keys:: Keys in the character backend multiplexer
* pcsys_monitor:: QEMU Monitor
* disk_images:: Disk Images
* pcsys_network:: Network emulation
@ -272,7 +273,7 @@ targets do not need a disk image.
@c man end
@node pcsys_keys
@section Keys
@section Keys in the graphical frontends
@c man begin OPTIONS
@ -322,15 +323,23 @@ Toggle mouse and keyboard grab.
In the virtual consoles, you can use @key{Ctrl-Up}, @key{Ctrl-Down},
@key{Ctrl-PageUp} and @key{Ctrl-PageDown} to move in the back log.
@kindex Ctrl-a h
During emulation, if you are using the @option{-nographic} option, use
@key{Ctrl-a h} to get terminal commands:
@c man end
@node mux_keys
@section Keys in the character backend multiplexer
@c man begin OPTIONS
During emulation, if you are using a character backend multiplexer
(which is the default if you are using @option{-nographic}) then
several commands are available via an escape sequence. These
key sequences all start with an escape character, which is @key{Ctrl-a}
by default, but can be changed with @option{-echr}. The list below assumes
you're using the default.
@table @key
@item Ctrl-a h
@kindex Ctrl-a h
@item Ctrl-a ?
@kindex Ctrl-a ?
Print this help
@item Ctrl-a x
@kindex Ctrl-a x
@ -346,10 +355,11 @@ Toggle console timestamps
Send break (magic sysrq in Linux)
@item Ctrl-a c
@kindex Ctrl-a c
Switch between console and monitor
Rotate between the frontends connected to the multiplexer (usually
this switches between the monitor and the console)
@item Ctrl-a Ctrl-a
@kindex Ctrl-a a
Send Ctrl-a
@kindex Ctrl-a Ctrl-a
Send the escape character to the frontend
@end table
@c man end

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@ -2162,8 +2162,49 @@ All devices must have an id, which can be any string up to 127 characters long.
It is used to uniquely identify this device in other command line directives.
A character device may be used in multiplexing mode by multiple front-ends.
The key sequence of @key{Control-a} and @key{c} will rotate the input focus
between attached front-ends. Specify @option{mux=on} to enable this mode.
Specify @option{mux=on} to enable this mode.
A multiplexer is a "1:N" device, and here the "1" end is your specified chardev
backend, and the "N" end is the various parts of QEMU that can talk to a chardev.
If you create a chardev with @option{id=myid} and @option{mux=on}, QEMU will
create a multiplexer with your specified ID, and you can then configure multiple
front ends to use that chardev ID for their input/output. Up to four different
front ends can be connected to a single multiplexed chardev. (Without
multiplexing enabled, a chardev can only be used by a single front end.)
For instance you could use this to allow a single stdio chardev to be used by
two serial ports and the QEMU monitor:
@example
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline,default \
-serial chardev:char0 \
-serial chardev:char0
@end example
You can have more than one multiplexer in a system configuration; for instance
you could have a TCP port multiplexed between UART 0 and UART 1, and stdio
multiplexed between the QEMU monitor and a parallel port:
@example
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline,default \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1
@end example
When you're using a multiplexed character device, some escape sequences are
interpreted in the input. @xref{mux_keys, Keys in the character backend
multiplexer}.
Note that some other command line options may implicitly create multiplexed
character backends; for instance @option{-serial mon:stdio} creates a
multiplexed stdio backend connected to the serial port and the QEMU monitor,
and @option{-nographic} also multiplexes the console and the monitor to
stdio.
There is currently no support for multiplexing in the other direction
(where a single QEMU front end takes input and output from multiple chardevs).
Every backend supports the @option{logfile} option, which supplies the path
to a file to record all data transmitted via the backend. The @option{logappend}