drm/vkms: Use offset-adjusted shadow-plane mappings and output

For framebuffers with non-zero offset fields, shadow-plane helpers
provide a pointer to the first byte of the contained data. Use it in
vkms.

Also provide use the offset-adjusted data address for the writeback
job's output buffers. Output framebuffers with non-zero offsets now
have their content written to the correct location.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Acked-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/vkms/vkms_composer.c

···
 		return;
 
 	if (wb_pending)
-		vaddr_out = crtc_state->active_writeback->map[0].vaddr;
+		vaddr_out = crtc_state->active_writeback->data[0].vaddr;
 
 	ret = compose_active_planes(&vaddr_out, primary_composer,
 				    crtc_state);

drivers/gpu/drm/vkms/vkms_drv.h

···
 
 struct vkms_writeback_job {
 	struct dma_buf_map map[DRM_FORMAT_MAX_PLANES];
+	struct dma_buf_map data[DRM_FORMAT_MAX_PLANES];
 };
 
 struct vkms_composer {

drivers/gpu/drm/vkms/vkms_plane.c

···
 	memcpy(&composer->src, &new_state->src, sizeof(struct drm_rect));
 	memcpy(&composer->dst, &new_state->dst, sizeof(struct drm_rect));
 	memcpy(&composer->fb, fb, sizeof(struct drm_framebuffer));
-	memcpy(&composer->map, &shadow_plane_state->map, sizeof(composer->map));
+	memcpy(&composer->map, &shadow_plane_state->data, sizeof(composer->map));
 	drm_framebuffer_get(&composer->fb);
 	composer->offset = fb->offsets[0];
 	composer->pitch = fb->pitches[0];

drivers/gpu/drm/vkms/vkms_writeback.c

···
 	if (!vkmsjob)
 		return -ENOMEM;
 
-	ret = drm_gem_fb_vmap(job->fb, vkmsjob->map, NULL);
+	ret = drm_gem_fb_vmap(job->fb, vkmsjob->map, vkmsjob->data);
 	if (ret) {
 		DRM_ERROR("vmap failed: %d\n", ret);
 		goto err_kfree;