drm: vkms: get the reference to `drm_framebuffer` instead if coping it

Instead of coping `drm_framebuffer` - which can cause problems -
we just get the reference and add the ref count.
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Igor Torrente <igormtorrente@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905190811.25024-5-igormtorrente@gmail.com

drivers/gpu/drm/vkms/vkms_composer.c

@@ -153,7 +153,7 @@ static void compose_plane(struct vkms_frame_info *primary_plane_info,
 			  struct vkms_frame_info *plane_frame_info,
 			  void *vaddr_out)
 {
-	struct drm_framebuffer *fb = &plane_frame_info->fb;
+	struct drm_framebuffer *fb = plane_frame_info->fb;
 	void *vaddr;
 	void (*pixel_blend)(const u8 *p_src, u8 *p_dst);
 
@@ -175,7 +175,7 @@ static int compose_active_planes(void **vaddr_out,
 				 struct vkms_frame_info *primary_plane_info,
 				 struct vkms_crtc_state *crtc_state)
 {
-	struct drm_framebuffer *fb = &primary_plane_info->fb;
+	struct drm_framebuffer *fb = primary_plane_info->fb;
 	struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
 	const void *vaddr;
 	int i;

drivers/gpu/drm/vkms/vkms_drv.h

@@ -29,7 +29,7 @@ struct vkms_writeback_job {
 };
 
 struct vkms_frame_info {
-	struct drm_framebuffer fb;
+	struct drm_framebuffer *fb;
 	struct drm_rect src, dst;
 	struct iosys_map map[DRM_FORMAT_MAX_PLANES];
 	unsigned int offset;

drivers/gpu/drm/vkms/vkms_plane.c

@@ -49,12 +49,12 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
 	struct vkms_plane_state *vkms_state = to_vkms_plane_state(old_state);
 	struct drm_crtc *crtc = vkms_state->base.base.crtc;
 
-	if (crtc) {
+	if (crtc && vkms_state->frame_info->fb) {
 		/* dropping the reference we acquired in
 		 * vkms_primary_plane_update()
 		 */
-		if (drm_framebuffer_read_refcount(&vkms_state->frame_info->fb))
-			drm_framebuffer_put(&vkms_state->frame_info->fb);
+		if (drm_framebuffer_read_refcount(vkms_state->frame_info->fb))
+			drm_framebuffer_put(vkms_state->frame_info->fb);
 	}
 
 	kfree(vkms_state->frame_info);
@@ -109,9 +109,9 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
 	frame_info = vkms_plane_state->frame_info;
 	memcpy(&frame_info->src, &new_state->src, sizeof(struct drm_rect));
 	memcpy(&frame_info->dst, &new_state->dst, sizeof(struct drm_rect));
-	memcpy(&frame_info->fb, fb, sizeof(struct drm_framebuffer));
+	frame_info->fb = fb;
 	memcpy(&frame_info->map, &shadow_plane_state->data, sizeof(frame_info->map));
-	drm_framebuffer_get(&frame_info->fb);
+	drm_framebuffer_get(frame_info->fb);
 	frame_info->offset = fb->offsets[0];
 	frame_info->pitch = fb->pitches[0];
 	frame_info->cpp = fb->format->cpp[0];