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Subject: Re: [PATCH v6 4/6] vfio: Define vfio based vgpu's dma-buf operations
From: Gerd Hoffmann <kraxel@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Chen, Xiaoguang" <xiaoguang.chen@intel.com>
Cc: "chris@chris-wilson.co.uk" <chris@chris-wilson.co.uk>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "zhenyuw@linux.intel.com" <zhenyuw@linux.intel.com>,
        "Lv, Zhiyuan" <zhiyuan.lv@intel.com>,
        "intel-gvt-dev@lists.freedesktop.org" 
        <intel-gvt-dev@lists.freedesktop.org>,
        "Wang, Zhi A" <zhi.a.wang@intel.com>,
        "Tian, Kevin" <kevin.tian@intel.com>
Date: Fri, 02 Jun 2017 10:38:12 +0200
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> struct vfio_vgpu_surface_info {
>         __u64 start;
>         __u32 width;
>         __u32 height;
>         __u32 stride;
>         __u32 size;
>         __u32 x_pos;
>         __u32 y_pos;
>         __u32 padding;
>         /* Only used when VFIO_VGPU_SURFACE_DMABUF_* flags set */
>         __u64 drm_format_mod;
>         __u32 drm_format;

Why for dmabufs only?  Shouldn't the region specify the format too? 
Even in case you are using a fixed one (say DRM_FORMAT_XRGB8888) you
can explicitly say so in drm_format (and set drm_format_mod to zero).

cheers,
  Gerd