[PATCH weston v5 16/42] compositor-drm: Refcount drm_fb

[Daniel Stone]

Sometimes we need to duplicate an existing drm_fb, e.g. when
pageflipping to the same buffer to kickstart the repaint loop. To handle
situations like these, and simplify resource management for dumb and
cursor buffers, refcount drm_fb.

Signed-off-by: Daniel Stone <daniels at collabora.com>

Differential Revision: https://phabricator.freedesktop.org/D1491
---
 libweston/compositor-drm.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
index aaf871d..6f4a873 100644
--- a/libweston/compositor-drm.c
+++ b/libweston/compositor-drm.c
@@ -137,6 +137,8 @@ struct drm_fb {
 		BUFFER_GBM_SURFACE, /**< internal EGL rendering */
 	} type;
 
+	int refcnt;
+
 	uint32_t fb_id, stride, handle, size;
 	int width, height;
 	int fd;
@@ -299,6 +301,8 @@ drm_fb_create_dumb(struct drm_backend *b, int width, int height,
 	if (!fb)
 		return NULL;
 
+	fb->refcnt = 1;
+
 	switch (format) {
 		case GBM_FORMAT_XRGB8888:
 			bpp = 32;
@@ -379,6 +383,13 @@ err_fb:
 }
 
 static struct drm_fb *
+drm_fb_ref(struct drm_fb *fb)
+{
+	fb->refcnt++;
+	return fb;
+}
+
+static struct drm_fb *
 drm_fb_get_from_bo(struct gbm_bo *bo,
 		   struct drm_backend *backend, uint32_t format)
 {
@@ -387,12 +398,13 @@ drm_fb_get_from_bo(struct gbm_bo *bo,
 	int ret;
 
 	if (fb)
-		return fb;
+		return drm_fb_ref(fb);
 
 	fb = zalloc(sizeof *fb);
 	if (fb == NULL)
 		return NULL;
 
+	fb->refcnt = 1;
 	fb->bo = bo;
 
 	fb->width = gbm_bo_get_width(bo);
@@ -458,6 +470,10 @@ drm_fb_unref(struct drm_fb *fb)
 	if (!fb)
 		return;
 
+	assert(fb->refcnt > 0);
+	if (--fb->refcnt > 0)
+		return;
+
 	switch (fb->type) {
 	case BUFFER_PIXMAN_DUMB:
 		/* nothing: pixman buffers are destroyed manually */
-- 
2.9.3