[PATCH weston 19/68] 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.

Differential Revision: https://phabricator.freedesktop.org/D1491

Signed-off-by: Daniel Stone <daniels at collabora.com>
---
 libweston/compositor-drm.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
index eb735b2..a684ac9 100644
--- a/libweston/compositor-drm.c
+++ b/libweston/compositor-drm.c
@@ -140,6 +140,8 @@ enum drm_fb_type {
 struct drm_fb {
 	enum drm_fb_type type;
 
+	int refcnt;
+
 	uint32_t fb_id, stride, handle, size;
 	const struct pixel_format_info *format;
 	int width, height;
@@ -302,6 +304,8 @@ drm_fb_create_dumb(struct drm_backend *b, int width, int height,
 	if (!fb)
 		return NULL;
 
+	fb->refcnt = 1;
+
 	fb->format = pixel_format_get_info(format);
 	if (!fb->format) {
 		weston_log("failed to look up format 0x%lx\n",
@@ -312,6 +316,7 @@ drm_fb_create_dumb(struct drm_backend *b, int width, int height,
 	if (!fb->format->depth || !fb->format->bpp) {
 		weston_log("format 0x%lx is not compatible with dumb buffers\n",
 			   (unsigned long) format);
+		goto err_fb;
 	}
 
 	memset(&create_arg, 0, sizeof create_arg);
@@ -384,6 +389,13 @@ 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, enum drm_fb_type type)
 {
@@ -392,13 +404,14 @@ drm_fb_get_from_bo(struct gbm_bo *bo, struct drm_backend *backend,
 	int ret;
 
 	if (fb)
-		return fb;
+		return drm_fb_ref(fb);
 
 	fb = zalloc(sizeof *fb);
 	if (fb == NULL)
 		return NULL;
 
 	fb->type = type;
+	fb->refcnt = 1;
 	fb->bo = bo;
 
 	fb->width = gbm_bo_get_width(bo);
@@ -472,6 +485,10 @@ 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