diff options
Diffstat (limited to 'qemu-options.hx')
| -rw-r--r-- | qemu-options.hx | 45 |
1 files changed, 43 insertions, 2 deletions
diff --git a/qemu-options.hx b/qemu-options.hx index f528405810..599db9474c 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -2166,8 +2166,49 @@ 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} |