drm/gud: Get offset-adjusted mapping from drm_gem_fb_vmap()

Pass the data parameter to drm_gem_fb_vmap() to retrieve pointers
to the data. This address is different from the mapping addresses
for framebuffers with non-zero offsets. Replaces gud's internal
computation.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210803125928.27780-4-tzimmermann@suse.de

drivers/gpu/drm/gud/gud_pipe.c

@@ -153,6 +153,7 @@ static int gud_prep_flush(struct gud_device *gdrm, struct drm_framebuffer *fb,
 	struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;
 	u8 compression = gdrm->compression;
 	struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
+	struct dma_buf_map map_data[DRM_FORMAT_MAX_PLANES];
 	void *vaddr, *buf;
 	size_t pitch, len;
 	int ret = 0;
@@ -162,11 +163,11 @@ static int gud_prep_flush(struct gud_device *gdrm, struct drm_framebuffer *fb,
 	if (len > gdrm->bulk_len)
 		return -E2BIG;
 
-	ret = drm_gem_fb_vmap(fb, map, NULL);
+	ret = drm_gem_fb_vmap(fb, map, map_data);
 	if (ret)
 		return ret;
 
-	vaddr = map[0].vaddr + fb->offsets[0];
+	vaddr = map_data[0].vaddr;
 
 	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
 	if (ret)