This adds a few lines describing multiplexer configuration for
multiplexing several backend devices with a single frontend
device.
Signed-off-by: Roman Penyaev <r.peni...@gmail.com>
Cc: "Marc-André Lureau" <marcandre.lur...@redhat.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: qemu-devel@nongnu.org
---
qemu-options.hx | 44 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 40 insertions(+), 4 deletions(-)
diff --git a/qemu-options.hx b/qemu-options.hx
index d94e2cbbaeb1..de1d540b85cd 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3782,7 +3782,7 @@ SRST
The general form of a character device option is:
``-chardev backend,id=id[,mux=on|off][,options]``
- Backend is one of: ``null``, ``socket``, ``udp``, ``msmouse``,
+ Backend is one of: ``null``, ``socket``, ``udp``, ``msmouse``, ``mux``,
``vc``, ``ringbuf``, ``file``, ``pipe``, ``console``, ``serial``,
``pty``, ``stdio``, ``braille``, ``parallel``,
``spicevmc``, ``spiceport``. The specific backend will determine the
@@ -3839,9 +3839,9 @@ The general form of a character device option is:
the QEMU monitor, and ``-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).
+ If you need to multiplex in the opposite direction (where one QEMU
+ interface receives input and output from multiple chardev devices),
+ please refer to the paragraph below regarding chardev mux configuration.
Every backend supports the ``logfile`` option, which supplies the
path to a file to record all data transmitted via the backend. The
@@ -3941,6 +3941,42 @@ The available backends are:
Forward QEMU's emulated msmouse events to the guest. ``msmouse``
does not take any options.
+``-chardev mux,id=id,chardev=chardev-id[,,chardev-idN]``
+ Explicitly create chardev multiplexer with possibility to multiplex
+ in the opposite direction, where one QEMU interface (frontend device)
+ receives input and output from multiple chardev backend devices.
+
+ For example the following is a use case of 2 backend devices: text
+ virtual console ``vc0`` and a socket ``sock0`` connected
+ to a single virtio hvc console frontend device with multiplexer
+ ``mux0`` help. Virtual console renders text to an image, which
+ can be shared over the VNC protocol, in turn socket backend provides
+ biderectional communication to the virtio hvc console over socket.
+ The example configuration can be the following:
+
+ ::
+
+ -chardev socket,path=/tmp/sock,server=on,wait=off,id=sock0 \
+ -chardev vc,id=vc0 \
+ -chardev mux,id=mux0,chardev=vc0,,sock0 \
+ -device virtconsole,chardev=mux0 \
+ -vnc 0.0.0.0:0
+
+ Once QEMU starts VNC client and any TTY emulator can be used to
+ control a single hvc console:
+
+ ::
+
+ # VNC client
+ vncviewer :0
+
+ # TTY emulator
+ socat unix:connect:/tmp/sock pty,link=/tmp/pty & \
+ tio /tmp/pty
+
+ Multiplexing of several backend devices with serveral frontend devices
+ is not supported.
+
``-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]``
Connect to a QEMU text console. ``vc`` may optionally be given a
specific size.
--
2.34.1
