Re: [PATCH v17 5/6] vfio: ABI for mdev display dma-buf operation

[Alex Williamson]

On Thu, 9 Nov 2017 19:35:14 +0100
Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:

>   Hi,
> 
> > struct vfio_device_gfx_plane_info lacks the head field we've been
> > discussing.  Thanks,  
> 
> Adding multihead support turned out to not be that easy.  There are
> corner cases like a single framebuffer spawning both heads.  Also it
> would be useful to somehow hint to the guest which heads it should use.
> 
> In short:  Proper multihead support is more complex than just adding a
> head field for later use.  So in a short private discussion with Tina we
> came to the conclusion that it will be better add multihead support to
> the API when the first driver wants use it, so we can actually test the
> interface and make sure we didn't miss anything.  Adding a incomplete
> multihead API now doesn't help anybody.

Do you think we can enable multi-head and preserve backwards
compatibility within this API proposed here?  Thanks,

Alex