How far away is a multi-head solution, do you think?
It sounds like most of the work is in the client and the X driver?
Noel
On Mon, May 7, 2012 at 12:28 AM, Alon Levy <alevy@xxxxxxxxxx> wrote:
> Hi,
>
> Currently we support multiple monitors by having:
> single pci = single display channel = single client window
>
> The RANDR architecture doesn't lend itself to this, but on the other hand it
> makes it very easy to have an alternative scheme:
> single pci = single display channel = multiple client windows
>
> RANDR introduces a concept of a CRTC and an OUTPUT. The CRTC scansout a
> portion of the framebuffer onto one or more OUTPUTs. I propose having a 1:1 CRTC:OUTPUT correspondence and introducing two new commands, one on PCI and one for the protocol:
> QXLHead = (id, x, y, width, height)
> SpiceHead = (id, x, y, width, height)
>
> 1. Guest enables a new monitor:
> 2. Guest pushes QXLHead command to command ring
> 3. Server sends SpiceHead message on the ring's display channel.
> 4. Client creates a window out of [x, y, width, height] scanning out of the primary surface (there is one associated primary with the display channel)
>
> Some other notes:
> a. To disable a monitor, send (id, 0, 0, 0, 0) (So there remain invalid range of
> values {(id, x, y, width, height) | max(x, y, width, height)!=0 and min(width,
> height) = 0})
> b. Guest keeps track of the head id.
> c. No idea if this is easy / natural for a WDDM driver, if not we will keep having multiple display channels there, or have to extend the concept of primary to have a number of primary surfaces. Another option is to extend the QXLHead/SpiceHead to have a surface id argument. But I suggest to postpone this to when we actually work on the WDDM driver (unless someone wants to look at it now).
> d. Improvements from this method are:
> single vram bar for multiple heads, single ram bar - more efficient memory allocation
> single display channel means single glz dictionary, single image cache, again more efficient.
> limit of 4 monitors is lifted (the limit of four display channels remains)
> implementation for guest is trivial:
> keep track of enclosing size of primary and resize it as needed
> issue a QXLHead for each output enabled / disabled (corresponds with crtc since we keep a 1:1 relation in the driver).
>
> I have a proof of concept driver, but needs some work yet. I want to get input on this scheme, it is also very related to application remoting, but I haven't given it thought so far.
>
> Alon Levy (2):
> qxl_dev: dynamic head support on single display channel
> protocol: add SPICE_DISPLAY_CAP_HEAD
>
> spice/protocol.h | 4 ++++
> spice/qxl_dev.h | 12 ++++++++++++
> 2 files changed, 16 insertions(+)
>
> --
> 1.7.10.1
>
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--
Noel Van Hook - Intelligraphics, Inc
522 Cooper Ave N
Red Lodge, MT 59068
Noel.Van.Hook@xxxxxxxxxxxxxxxxxxx (425) 770-5561
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