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

[Zhang, Tina]

> -----Original Message-----
> From: intel-gvt-dev [mailto:intel-gvt-dev-bounces at lists.freedesktop.org] On
> Behalf Of Zhenyu Wang
> Sent: Monday, July 17, 2017 10:27 AM
> To: Zhang, Tina <tina.zhang at intel.com>
> Cc: Tian, Kevin <kevin.tian at intel.com>; intel-gfx at lists.freedesktop.org;
> kwankhede at nvidia.com; zhenyuw at linux.intel.com; chris at chris-wilson.co.uk;
> alex.williamson at redhat.com; Lv, Zhiyuan <zhiyuan.lv at intel.com>;
> daniel at ffwll.ch; intel-gvt-dev at lists.freedesktop.org; Wang, Zhi A
> <zhi.a.wang at intel.com>; Gerd Hoffmann <kraxel at redhat.com>
> Subject: Re: [PATCH v11 1/1] vfio: ABI for mdev display dma-buf operation
> 
> On 2017.07.17 01:10:03 +0000, Zhang, Tina wrote:
> > > > +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 */
> > >
> > > DRM_FORMAT_*
> > >
> > > drm_format_mod is gone?  Not needed?
> > > How tiled buffers are handled then?
> > Drm_format_mod is used as one of the plane's characteristics when judging
> the dma-buf of the plane is new to expose or an old exposed one. As from V10
> we leave this comparing logic to kernel, user mode might not need this field any
> more. If user mode wants, this can be also got though drm APIs. For example,
> eglCreateImageKHR() uses drm APIs to get the tiling format, without asking the
> invoker to explicitly use it as a parameter.
> > Do you think this field is still needed?
> >
> 
> Of course we need that modifier for complete format info. Don't just think for
> i915 usage, there's possible modifier for other vendor driver, and it's required
> for e.g ADDFB2 in drm kms. Pls add it back in next version.
We definitely can add it back if it is thought to be useful. Just some curious, as we don't produce the content in the GEM buffer (a.k.a we just expose it here), why we need to know the tile mode. In addition, DRM API can support the functionality to get the tile mode ot GEM buffer. 

Thanks,
Tina
> 
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