On Tue, Jan 21, 2025 at 4:02 PM Alex Bennée <alex.ben...@linaro.org> wrote:
>
> Roman Penyaev <r.peni...@gmail.com> writes:
>
> > This adds a few lines describing `hub` aggregator configuration
> > for aggregation of 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: qemu-devel@nongnu.org
> > ---
> > qemu-options.hx | 48 ++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 44 insertions(+), 4 deletions(-)
> >
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 7090d59f6f10..fdc46f7e68b3 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -3720,7 +3720,7 @@ 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``, ``hub``,
> > ``vc``, ``ringbuf``, ``file``, ``pipe``, ``console``, ``serial``,
> > ``pty``, ``stdio``, ``braille``, ``parallel``,
> > ``spicevmc``, ``spiceport``. The specific backend will determine the
> > @@ -3777,9 +3777,10 @@ 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 aggregate data in the opposite direction (where one
> > + QEMU frontend interface receives input and output from multiple
> > + backend chardev devices), please refer to the paragraph below
> > + regarding chardev ``hub`` aggregator device configuration.
> >
> > Every backend supports the ``logfile`` option, which supplies the
> > path to a file to record all data transmitted via the backend. The
> > @@ -3879,6 +3880,45 @@ The available backends are:
> > Forward QEMU's emulated msmouse events to the guest. ``msmouse``
> > does not take any options.
> >
> > +``-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]`` Explicitly create
> > + chardev backend hub device with the possibility to aggregate input
> > + from multiple backend devices and forward it to a single frontend
> > + device. Additionally, `hub` device takes the output from the
> > + frontend device and sends it back to all the connected backend
> > + devices. This allows for seamless interaction between different
> > + backend devices and a single frontend interface. Aggregation
> > + supported for up to 4 chardev devices. (Since 10.0)
> > +
> > + For example, the following is a use case of 2 backend devices:
> > + virtual console ``vc0`` and a pseudo TTY ``pty0`` connected to
> > + a single virtio hvc console frontend device with a hub ``hub0``
> > + help. Virtual console renders text to an image, which can be
> > + shared over the VNC protocol. In turn, pty backend provides
> > + bidirectional communication to the virtio hvc console over the
> > + pseudo TTY file. The example configuration can be as follows:
> > +
> > + ::
> > +
> > + -chardev pty,path=/tmp/pty,id=pty0 \
> > + -chardev vc,id=vc0 \
> > + -chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \
> > + -device virtconsole,chardev=hub0 \
> > + -vnc 0.0.0.0:0
> > +
> > + Once QEMU starts VNC client and any TTY emulator can be used to
> > + control a single hvc console:
> > +
> > + ::
> > +
> > + # Start TTY emulator
> > + tio /tmp/pty
> > +
> > + # Start VNC client and switch to virtual console Ctrl-Alt-2
> > + vncviewer :0
> > +
> > + Several frontend devices is not supported. Stacking of multiplexers
> > + and hub devices is not supported as well.
> > +
>
> Not sure why this breaks but I'm seeing:
>
> FAILED: docs/docs.stamp
> /usr/bin/env CONFDIR=etc/qemu
> /home/alex/lsrc/qemu.git/builds/all/pyvenv/bin/sphinx-build -q -W
> -Dkerneldoc_werror=1 -j auto -Dversion=9.2.50 -Drelease=
> -Ddepfile=docs/docs.d -Ddepfile_stamp=docs/docs.stamp -b html -d
> /home/alex/lsrc/qemu.git/builds/all/docs/manual.p
> /home/alex/lsrc/qemu.git/docs /home/alex/lsrc/qemu.git/builds/all/docs/manual
>
> Warning, treated as error:
> /home/alex/lsrc/qemu.git/qemu-options.hx:3884:'any' reference target not
> found: hub
This is odd, my make is silent. Can you please check this?
diff --git a/qemu-options.hx b/qemu-options.hx
index fdc46f7e68b3..e6d9de142aaf 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3880,7 +3880,8 @@ The available backends are:
Forward QEMU's emulated msmouse events to the guest. ``msmouse``
does not take any options.
-``-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]`` Explicitly create
+``-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]``
+ Explicitly create
--
Roman
