[PATCH v11 1/1] vfio: ABI for mdev display dma-buf operation

[Zhang, Tina]

> -----Original Message-----
> From: Zhang, Tina
> Sent: Wednesday, July 12, 2017 2:11 PM
> To: alex.williamson at redhat.com; kraxel at redhat.com; chris at chris-wilson.co.uk;
> zhenyuw at linux.intel.com; Lv, Zhiyuan <zhiyuan.lv at intel.com>; Wang, Zhi A
> <zhi.a.wang at intel.com>; Tian, Kevin <kevin.tian at intel.com>; daniel at ffwll.ch;
> kwankhede at nvidia.com
> Cc: Zhang, Tina <tina.zhang at intel.com>; intel-gfx at lists.freedesktop.org; intel-
> gvt-dev at lists.freedesktop.org
> Subject: [PATCH v11 1/1] vfio: ABI for mdev display dma-buf operation
> 
> 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>
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index
> ae46105..c176cc8 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -502,6 +502,32 @@ 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 */
> +	__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*/
> +	__s32 fd;	/* dma-buf fd */
> +};
> +
I remove plane_id as I cannot find its meaning for dmabuf usage. Also, I don't know how it could be used by region usage.
So, if someone can explain its usage, I can add it back. Thanks.

Another open is, so far, our design is focused on dmabuf based gfx plane only. Can we go a step further to consider a general
Buffer sharing interface? If we reference V4L2, we can see dmabuf can be considered as one kind of buffers, we can have  more
kinds of buffers, like mmap buffer and so on. So, if we think about that, we may need another ioctl to ask the mdev device which
kind of buffer it supports, and then use the VFIO_DEVICE_QUERY_* ioctl to get it back for user mode accessing. Different kinds
of mdev devices can have different query ioctl name and structure. Is it reasonable?
Thanks.

Tina

> +#define VFIO_DEVICE_QUERY_GFX_PLANE _IO(VFIO_TYPE, VFIO_BASE + 14)
> +
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
> 
>  /**
> --
> 2.7.4