Re: [Qemu-devel] [PATCH 2/3] usb-redir: Call qemu_chr_guest_open/close

[Hans de Goede]

Hi,

On 08/07/2011 05:52 PM, Anthony Liguori wrote:
> On 08/07/2011 08:21 AM, Hans de Goede wrote:
> > To let the chardev now we're ready start receiving data. This is necessary
> > with the spicevmc chardev to get it registered with the spice-server.
> >
> > Signed-off-by: Hans de Goede<address@hidden>
> > ---
> > usb-redir.c | 3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> > diff --git a/usb-redir.c b/usb-redir.c
> > index e212993..ec88c0b 100644
> > --- a/usb-redir.c
> > +++ b/usb-redir.c
> > @@ -809,6 +809,8 @@ static int usbredir_initfn(USBDevice *udev)
> >
> > qemu_chr_add_handlers(dev->cs, usbredir_chardev_can_read,
> > usbredir_chardev_read, usbredir_chardev_event, dev);
> > + /* Let the other side know we are ready */
> > + qemu_chr_guest_open(dev->cs);
>
>
> You should do guest_open before adding handlers.

Erm, no, guest_open may lead to a callback in the
chardev, to which it may respond by immediately queuing a few writes /
doing a read. To me it makes much more sense to actually call guest_open
when we are ready to receive data / to be read from, rather then to do
it before our handlers are hooked up and thus before we are ready.

Regards,

Hans