> -----Original Message----- > From: intel-gvt-dev [mailto:intel-gvt-dev-bounces@xxxxxxxxxxxxxxxxxxxxx] On > Behalf Of Gerd Hoffmann > Sent: Friday, November 10, 2017 3:03 PM > To: Alex Williamson <alex.williamson@xxxxxxxxxx> > Cc: Tian, Kevin <kevin.tian@xxxxxxxxx>; Yuan, Hang <hang.yuan@xxxxxxxxx>; > Daniel Vetter <daniel.vetter@xxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; > joonas.lahtinen@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > zhenyuw@xxxxxxxxxxxxxxx; chris@xxxxxxxxxxxxxxxxxx; kwankhede@xxxxxxxxxx; > Lv, Zhiyuan <zhiyuan.lv@xxxxxxxxx>; daniel@xxxxxxxx; Zhang, Tina > <tina.zhang@xxxxxxxxx>; intel-gvt-dev@xxxxxxxxxxxxxxxxxxxxx; Wang, Zhi A > <zhi.a.wang@xxxxxxxxx> > Subject: Re: [PATCH v17 5/6] vfio: ABI for mdev display dma-buf operation > > On Thu, Nov 09, 2017 at 01:54:57PM -0700, Alex Williamson wrote: > > 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? > > Yes, I think we can. Adding new fields is possible thanks to the argsz field at the > start of the struct, so we easily add the new fields (head, framebuffer rectangle, > whatever else is needed). If the new fields are not present the driver can simply > assume head=0. > > Does the driver set argsz too? If so userspace can detect whenever the driver > supports the multihead API extension (before going to probe for > head=1) that way. If not we probably need an additional probe flag for that. > But in any case I'm confident this is solvable. > > Passing hints about the display configuration to the guest needs a new ioctl, so > we don't have compatibility issues there. Thanks. So, do we all agree on this? If so, the next version will be submitted soon with some updated comments. Thanks. BR, Tina > > cheers, > Gerd > > _______________________________________________ > intel-gvt-dev mailing list > intel-gvt-dev@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
