Re: [PATCH 08/13] char: Add mux option to ChardevOptions

[Paolo Bonzini]

On 12/11/20 18:59, Kevin Wolf wrote:
> The final missing piece to achieve compatibility between
> qemu_chr_parse_cli_str()/qemu_chr_new_cli() and the legacy command line
> is support for the 'mux' option. Implement it.
>
> Signed-off-by: Kevin Wolf<kwolf@redhat.com>
> ---
>   qapi/char.json |  4 +++-
>   chardev/char.c | 41 +++++++++++++++++++++++++++++++++++------
>   2 files changed, 38 insertions(+), 7 deletions(-)
>
> diff --git a/qapi/char.json b/qapi/char.json
> index e1f9347044..d6733a5473 100644
> --- a/qapi/char.json
> +++ b/qapi/char.json
> @@ -453,12 +453,14 @@
>   #
>   # @id: the chardev's ID, must be unique
>   # @backend: backend type and parameters
> +# @mux: enable multiplexing mode (default: false)
>   #
>   # Since: 6.0
>   ##
>   { 'struct': 'ChardevOptions',
>     'data': { 'id': 'str',
> -            'backend': 'ChardevBackend' },
> +            'backend': 'ChardevBackend',
> +            '*mux': 'bool' },
>     'aliases': [ { 'source': ['backend'] } ] }
>   

I think this shows that -chardev and chardev-add are both kind of 
unrepairable.  The right way to do a mux with a serial and monitor on 
top should be explicit:

            stdio
               ↑
         mux-controller
          ↑        ↑
         mux      mux
          ↑        ↑
       serial   monitor

        -object chardev-stdio,id=stdio
        -object chardev-mux-controller,id=mux,backend=stdio
        -object chardev-mux,id=serial-chardev,controller=mux
        -object chardev-mux,id=mon-chardev,controller=mux
        -serial chardev:serial-chardev
        -monitor chardev:mon-chardev

Adding automagic "mux" creation to -chardev is wrong.  I don't entirely 
object to the series since it's quite nice, but I see it as more of a 
cleanup than the final stage.  It hinges on what Markus thinks of 
aliases, I guess.

Paolo