drm/xen-front: Pass dumb buffer data offset to the backend

While importing a dmabuf it is possible that the data of the buffer
is put with offset which is indicated by the SGT offset.
Respect the offset value and forward it to the backend.

Signed-off-by: Oleksandr Andrushchenko <[e-mail]>
Acked-by: Noralf Trønnes <[e-mail]>
Signed-off-by: Juergen Gross <[e-mail]>

drivers/gpu/drm/xen/xen_drm_front.c

···
 
 int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
 			      u64 dbuf_cookie, u32 width, u32 height,
-			      u32 bpp, u64 size, struct page **pages)
+			      u32 bpp, u64 size, u32 offset,
+			      struct page **pages)
 {
 	struct xen_drm_front_evtchnl *evtchnl;
 	struct xen_drm_front_dbuf *dbuf;
···
 	req->op.dbuf_create.gref_directory =
 			xen_front_pgdir_shbuf_get_dir_start(&dbuf->shbuf);
 	req->op.dbuf_create.buffer_sz = size;
+	req->op.dbuf_create.data_ofs = offset;
 	req->op.dbuf_create.dbuf_cookie = dbuf_cookie;
 	req->op.dbuf_create.width = width;
 	req->op.dbuf_create.height = height;
···
 	ret = xen_drm_front_dbuf_create(drm_info->front_info,
 					xen_drm_front_dbuf_to_cookie(obj),
 					args->width, args->height, args->bpp,
-					args->size,
+					args->size, 0,
 					xen_drm_front_gem_get_pages(obj));
 	if (ret)
 		goto fail_backend;

drivers/gpu/drm/xen/xen_drm_front.h

···
 
 int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
 			      u64 dbuf_cookie, u32 width, u32 height,
-			      u32 bpp, u64 size, struct page **pages);
+			      u32 bpp, u64 size, u32 offset, struct page **pages);
 
 int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
 			    u64 dbuf_cookie, u64 fb_cookie, u32 width,

drivers/gpu/drm/xen/xen_drm_front_gem.c

···
 
 	ret = xen_drm_front_dbuf_create(drm_info->front_info,
 					xen_drm_front_dbuf_to_cookie(&xen_obj->base),
-					0, 0, 0, size, xen_obj->pages);
+					0, 0, 0, size, sgt->sgl->offset,
+					xen_obj->pages);
 	if (ret < 0)
 		return ERR_PTR(ret);