From a40db1b36ba3cf4c8599178740511d7d5c0c9641 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 16 Feb 2016 17:28:58 +0000 Subject: [PATCH] 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 Message-Id: <1455643738-6068-1-git-send-email-peter.maydell@linaro.org> Signed-off-by: Paolo Bonzini --- qemu-doc.texi | 30 ++++++++++++++++++++---------- qemu-options.hx | 45 +++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 63 insertions(+), 12 deletions(-) diff --git a/qemu-doc.texi b/qemu-doc.texi index c324da8b61..bc9dd13cc9 100644 --- a/qemu-doc.texi +++ b/qemu-doc.texi @@ -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 diff --git a/qemu-options.hx b/qemu-options.hx index 2f0465eeb1..7e6762ed19 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -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}