Re: [Qemu-devel] [PATCH] chardev: add baud parameter for serial host device

[Peter Wu]

On Saturday 15 June 2013 16:14:23 Eric Blake wrote:
> On 06/08/2013 10:49 PM, Peter Wu wrote:
> > When QEMU starts, it always changes the serial port parameters including
> > baud rate. This confused my guest which thought it was outputting at 9600
> > baud while it was in fact changed to 115200.
> > 
> > After this patch, I can use `-serial /dev/ttyS0,baud=9600` to override the
> > default baud rate of 115200. Documentation is updated as well, so that
> > users know about the new `baud` parameter for `-serial` and `-chardev
> > serial` (and its alias `-chardev tty`).
> > 
> > Note that the baud option is not implemented for Windows. QEMU does not
> > change the default baud rate on Windows anyway. If somebody is going to
> > implement it, do not forget to update the documentation on "COM" devices
> > which is also of backend serial.
> > 
> > Signed-off-by: Peter Wu <address@hidden>
> > ---
> > 
> > +++ b/qapi-schema.json
> > @@ -3186,7 +3186,7 @@
> > 
> >  # Configuration info for device and pipe chardevs.
> >  #
> >  # @device: The name of the special file for the device,
> > 
> > -#          i.e. /dev/ttyS0 on Unix or COM1: on Windows
> > +#          i.e. /dev/parport0 on Unix.
> > 
> >  # @type: What kind of device this is.
> >  #
> >  # Since: 1.4
> > 
> > @@ -3194,6 +3194,20 @@
> > 
> >  { 'type': 'ChardevHostdev', 'data': { 'device' : 'str' } }
> >  
> >  ##
> > 
> > +# @ChardevSerial
> > +#
> > +# Configuration info for serial chardevs.
> > +#
> > +# @device: The name of the special file for the device,
> > +#          i.e. /dev/ttyS0 on Unix or COM1: on Windows
> > +# @baud: #optional baud rate to set for host device. (default 115200)
> > +#
> > +# Since: 1.5
> > +##
> > +{ 'type': 'ChardevSerial', 'data': { 'device' : 'str',
> > +                                     '*baud': 'int' } }
> 
> Slick trick.  However, 1.5 is already released, so it is now since 1.6,
Well, it was worth trying :-P Anyway, I do not mind if the patch is edited to 
have 1.6 instead 1.5. Do you want me to send a new patch just for this tiny 
change or will you edit it before applying? (perhaps after adding a note to 
the commit message)

> and furthermore...
> 
> > +
> > +##
> > 
> >  # @ChardevSocket:
> >  #
> >  # Configuration info for (stream) socket chardevs.
> > 
> > @@ -3311,7 +3325,7 @@
> > 
> >  { 'type': 'ChardevDummy', 'data': { } }
> >  
> >  { 'union': 'ChardevBackend', 'data': { 'file'   : 'ChardevFile',
> > 
> > -                                       'serial' : 'ChardevHostdev',
> > +                                       'serial' : 'ChardevSerial',
> 
> without introspection, libvirt has no idea whether 'baud' is supported
> in the qemu it is talking to, other than trying and failing when talking
> to older qemu.  This patch forms yet another reason why libvirt wants to
> learn when we add optional parameters to a pre-existing QMP command.

I have do not use libvirt, do you want me to do further things for this patch 
to get accepted? Or is it more a side-note?

Regards,
Peter

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