Am Sonntag, den 09.11.2014, 16:51 +0100 schrieb Guennadi Liakhovetski:
> On Sun, 9 Nov 2014, Philipp Zabel wrote:
>
> > Hi Guennadi,
> >
> > On Fri, Nov 07, 2014 at 11:06:21PM +0100, Guennadi Liakhovetski wrote:
> > > Hi Philipp,
> > >
> > > Thanks for the patch and sorry for a late reply. I did look at your
> > > patches earlier too, but maybe not attentively enough, or maybe I'm
> > > misunderstanding something now. In the scan_of_host() function in
> > > soc_camera.c as of current -next I see:
> > >
> > > epn = of_graph_get_next_endpoint(np, epn);
> > >
> > > which already looks like a refcount leak to me. If epn != NULL, its
> > > refcount is incremented, but then immediately the variable gets
> > > overwritten, and there's no extra copy of that variable to fix this. If
> > > I'm right, then that bug in itself should be fixed, ideally before your
> > > patch is applied. But in fact, your patch fixes this, since it modifies
> > > of_graph_get_next_endpoint() to return with prev's refcount not
> > > incremented, right? Whereas the of_node_put(epn) later down in
> > > scan_of_host() decrements refcount of the _next_ endpoint, not the
> > > previous one, so, it should be left alone? I.e. AFAICT your modification
> > > to of_graph_get_next_endpoint() fixes soc_camera.c with no further
> > > modifications to it required?
> >
> > You are right. With the old implementation, you'd have to do the
> > epn = of_graph_get_next_endpoint(np, prev); of_node_put(prev); prev = epn;
> > dance to avoid leaking a reference to the first endpoint. This series
> > accidentally fixes soc_camera by changing of_graph_get_next_endpoint
> > to decrement the reference count itself.
>
> Right, so, the patch has to be adjusted not to touch soc_camera.c at all.
No. As of the current media-tree we still need move the of_node_put(epn)
out of the loop:
diff --git a/drivers/media/platform/soc_camera/soc_camera.c
b/drivers/media/platform/soc_camera/soc_camera.c
index f4308fe..619b2d4 100644
--- a/drivers/media/platform/soc_camera/soc_camera.c
+++ b/drivers/media/platform/soc_camera/soc_camera.c
@@ -1696,7 +1696,6 @@ static void scan_of_host(struct soc_camera_host *ici)
if (!i)
soc_of_bind(ici, epn, ren->parent);
- of_node_put(epn);
of_node_put(ren);
if (i) {
@@ -1704,6 +1703,8 @@ static void scan_of_host(struct soc_camera_host *ici)
break;
}
}
+
+ of_node_put(epn);
}
#else
We can do this in two steps (step 1 fixing the current status quo, step
2 as part of this series). Step 1:
--- a/drivers/media/platform/soc_camera/soc_camera.c
+++ b/drivers/media/platform/soc_camera/soc_camera.c
@@ -1691,11 +1691,13 @@ static void scan_of_host(struct soc_camera_host *ici)
{
struct device *dev = ici->v4l2_dev.dev;
struct device_node *np = dev->of_node;
- struct device_node *epn = NULL, *ren;
+ struct device_node *epn, *prev = NULL, *ren;
unsigned int i;
for (i = 0; ; i++) {
- epn = of_graph_get_next_endpoint(np, epn);
+ epn = of_graph_get_next_endpoint(np, prev);
+ of_node_put(prev);
+ prev = epn;
if (!epn)
break;
@@ -1710,7 +1712,6 @@ static void scan_of_host(struct soc_camera_host *ici)
if (!i)
soc_of_bind(ici, epn, ren->parent);
- of_node_put(epn);
of_node_put(ren);
if (i) {
And step 2:
diff --git a/drivers/media/platform/soc_camera/soc_camera.c
b/drivers/media/platform/soc_camera/soc_camera.c
index 3d44773..1de62bf 100644
--- a/drivers/media/platform/soc_camera/soc_camera.c
+++ b/drivers/media/platform/soc_camera/soc_camera.c
@@ -1691,13 +1691,11 @@ static void scan_of_host(struct soc_camera_host *ici)
{
struct device *dev = ici->v4l2_dev.dev;
struct device_node *np = dev->of_node;
- struct device_node *epn, *prev = NULL, *ren;
+ struct device_node *epn = NULL, *ren;
unsigned int i;
for (i = 0; ; i++) {
- epn = of_graph_get_next_endpoint(np, prev);
- of_node_put(prev);
- prev = epn;
+ epn = of_graph_get_next_endpoint(np, epn);
if (!epn)
break;
@@ -1719,6 +1717,8 @@ static void scan_of_host(struct soc_camera_host *ici)
break;
}
}
+
+ of_node_put(epn);
}
#else
Would you prefer that option?
regards
Philipp
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