From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38506) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aViMU-0003FA-QM for qemu-devel@nongnu.org; Tue, 16 Feb 2016 11:20:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aViMT-0003Le-Q3 for qemu-devel@nongnu.org; Tue, 16 Feb 2016 11:20:26 -0500 Sender: Paolo Bonzini References: <1455638581-5912-1-git-send-email-peter.maydell@linaro.org> From: Paolo Bonzini Message-ID: <56C34C40.2080407@redhat.com> Date: Tue, 16 Feb 2016 17:20:16 +0100 MIME-Version: 1.0 In-Reply-To: <1455638581-5912-1-git-send-email-peter.maydell@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qemu-options.hx: Improve documentation of chardev multiplexing mode List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell , qemu-devel@nongnu.org Cc: qemu-trivial@nongnu.org, Stefan Hajnoczi , patches@linaro.org On 16/02/2016 17:03, Peter Maydell wrote: > 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 > --- > There was some discussion on #qemu yesterday evening about multiplexing, > and "make the docs a bit less confusing" was one suggestion... > --- > qemu-options.hx | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/qemu-options.hx b/qemu-options.hx > index 2f0465e..6b46dd4 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -2162,8 +2162,26 @@ 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. > +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. > + > 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. > +of a multiplexed character device between attached front-ends. > + > +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. > + > +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} > Very nice, thanks! I'm queuing this patch. Paolo