[Spice-devel] [PATCH spice-protocol 2/8] Add the StreamMsgGraphicsDeviceInfo message

[Jonathon Jongsma]

On Wed, 2019-01-09 at 12:43 +0100, Lukáš Hrázký wrote:
> On Wed, 2019-01-09 at 02:38 -0500, Frediano Ziglio wrote:
> > > 
> > > The message contains information about the graphics device and
> > > monitor
> > > belonging to a particular video stream (which maps to a channel)
> > > from
> > > the streaming agent.
> > > 
> > > Signed-off-by: Lukáš Hrázký <lhrazky at redhat.com>
> > > ---
> > >  spice/stream-device.h | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > > 
> > > diff --git a/spice/stream-device.h b/spice/stream-device.h
> > > index 6add42b..77d76af 100644
> > > --- a/spice/stream-device.h
> > > +++ b/spice/stream-device.h
> > > @@ -90,6 +90,8 @@ typedef enum StreamMsgType {
> > >      STREAM_TYPE_CURSOR_SET,
> > >      /* guest cursor position */
> > >      STREAM_TYPE_CURSOR_MOVE,
> > > +    /* the graphics device display information message (device
> > > address and
> > > display id) */
> > > +    STREAM_TYPE_DEVICE_DISPLAY_INFO,
> > >  } StreamMsgType;
> > >  
> > >  typedef enum StreamCapabilities {
> > > @@ -140,6 +142,13 @@ typedef struct StreamMsgData {
> > >      uint8_t data[0];
> > >  } StreamMsgData;
> > >  
> > > +typedef struct StreamMsgDeviceDisplayInfo {
> > 
> > No much documentation, when it is supposed to be sent?
> > In which state?
> > From the agent, from the server or both?
> 
> I'll add some documentation.
> 
> > No capabilities for a new message?
> 
> No, the streaming agent protocol is not stable yet. Better to not add
> a
> capability and make the code more complex if it's not necessary.
> We've
> discussed this before...
> 
> > > +    uint32_t id;
> > 
> > I suppose is not the same "device_display_id", not clear what is
> > it.
> 
> Right, this is basically the equivalent of monitor_id, here it is
> kind
> of the ID of the stream to which the display info belongs. It's
> basically just a sequence of 0, 1, 2, ... and since only a single
> stream/monitor is supported at the moment, only a single message of
> this type is sent and it has id = 0.
> 
> Suggestions how to name it? monitor_id? stream_id?

I think stream_id may be ok.

> 
> > > +    uint32_t device_display_id;
> > > +    uint32_t device_address_len;
> > 
> > No limit? Is 4gb fine? I suppose you want a length to be able to
> > extend the message in the future, otherwise you can use the size
> > of the message.
> 
> How do you want me to set a limit here? In a comment?
> 
> I initially had these wrapped in a message that contained an array of
> these, hence the length. It is still unclear how this will exactly
> work
> with multi-monitor support. This message is likely going to change
> with
> that... Should I change it now?

Personally I would not try to accomodate multimonitor until we know
what we need.

> 
> > > +    uint8_t device_address[0];  // a zero-terminated string
> > 
> > Encoding? Utf-8?
> 
> The contents are the address of the device, I don't think utf really
> matters here.

Well, the address format is defined as 

"pci/<DOMAIN>/<SLOT>.<FUNCTION>/.../<SLOT>.<FUNCTION>"

So, aside from the string "pci/", the rest is just hex numbers and
dots. So we don't need to encode a bunch of special characters, just
characters within the ASCII range. But I don't suppose it would hurt to
document it as utf-8...


> 
> > I suppose by "zero-terminated" you mean if not terminated is a
> > protocol violation.
> 
> Yes. Do you prefer something else?
> 
> Cheers,
> Lukas
> 
> > > +} StreamMsgDeviceDisplayInfo;
> > > +
> > >  /* Tell to stop current stream and possibly start a new one.
> > >   * This message is sent by the host to the guest.
> > >   * Allows to communicate the codecs supported by the clients.
> > 
> > Frediano
> 
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