[Intel-gfx] [PATCH v13 5/7] vfio: ABI for mdev display dma-buf operation

[Zhang, Tina]

> -----Original Message-----
> From: dri-devel [mailto:dri-devel-bounces at lists.freedesktop.org] On Behalf Of
> Alex Williamson
> Sent: Wednesday, August 2, 2017 5:18 AM
> To: Zhang, Tina <tina.zhang at intel.com>
> Cc: Tian, Kevin <kevin.tian at intel.com>; kraxel at redhat.com; intel-
> gfx at lists.freedesktop.org; Wang, Zhi A <zhi.a.wang at intel.com>;
> kwankhede at nvidia.com; dri-devel at lists.freedesktop.org; intel-gvt-
> dev at lists.freedesktop.org; Lv, Zhiyuan <zhiyuan.lv at intel.com>
> Subject: Re: [PATCH v13 5/7] vfio: ABI for mdev display dma-buf operation
> 
> On Tue, 25 Jul 2017 17:28:18 +0800
> Tina Zhang <tina.zhang at intel.com> wrote:
> 
> > Add VFIO_DEVICE_QUERY_GFX_PLANE ioctl command to let user mode query
> > and get the plan and its related information.
> >
> > The dma-buf's life cycle is handled by user mode and tracked by kernel.
> > The returned fd in struct vfio_device_query_gfx_plane can be a new fd
> > or an old fd of a re-exported dma-buf. Host User mode can check the
> > value of fd and to see if it needs to create new resource according to
> > the new fd or just use the existed resource related to the old fd.
> >
> > Signed-off-by: Tina Zhang <tina.zhang at intel.com>
> > ---
> >  include/uapi/linux/vfio.h | 28 ++++++++++++++++++++++++++++
> >  1 file changed, 28 insertions(+)
> >
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index ae46105..827a230 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -502,6 +502,34 @@ struct vfio_pci_hot_reset {
> >
> >  #define VFIO_DEVICE_PCI_HOT_RESET	_IO(VFIO_TYPE, VFIO_BASE +
> 13)
> >
> > +/**
> > + * VFIO_DEVICE_QUERY_GFX_PLANE - _IOW(VFIO_TYPE, VFIO_BASE + 14,
> > +struct vfio_device_query_gfx_plane)
> > + *
> > + * Set the drm_plane_type and retrieve information about the gfx plane.
> > + *
> > + * Return: 0 on success, -errno on failure.
> > + */
> > +struct vfio_device_gfx_plane_info {
> > +	__u32 argsz;
> > +	__u32 flags;
> > +	/* in */
> > +	__u32 drm_plane_type;	/* type of plane: DRM_PLANE_TYPE_* */
> > +	/* out */
> > +	__u32 drm_format;	/* drm format of plane */
> > +	__u64 drm_format_mod;   /* tiled mode */
> > +	__u32 width;	/* width of plane */
> > +	__u32 height;	/* height of plane */
> > +	__u32 stride;	/* stride of plane */
> > +	__u32 size;	/* size of plane in bytes, align on page*/
> > +	__u32 x_pos;	/* horizontal position of cursor plane, upper left corner
> in pixels */
> > +	__u32 y_pos;	/* vertical position of cursor plane, upper left corner in
> lines*/
> > +	__u32 region_index;
> > +	__s32 fd;	/* dma-buf fd */
> 
> How do I know which of these is valid, region_index or fd?  Can I ask for one vs
> the other?  What are the errno values to differentiate unsupported vs not
> initialized?  Is there a "probe" flag that I can use to determine what the device
> supports without allocating those resources yet?
Dma-buf won't use region_index, which means region_index is zero all the time for dma-buf usage. 
As we discussed, there won't be errno if not initialized, just keep all fields zero.
I will add the comments about these in the next version. Thanks

Tina

> 
> Kirti, does this otherwise meet your needs?
> 
> Thanks,
> Alex
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