of: Make devicetree sysfs update functions consistent.

All of the DT modification functions are split into two parts, the first
part manipulates the DT data structure, and the second part updates
sysfs, but the code isn't very consistent about how the second half is
called. They don't all enforce the same rules about when it is valid to
update sysfs, and there isn't any clarity on locking.

The transactional DT modification feature that is coming also needs
access to these functions so that it can perform all the structure
changes together, and then all the sysfs updates as a second stage
instead of doing each one at a time.

Fix up the second have by creating a separate __of_*_sysfs() function
for each of the helpers. The new functions have consistent naming (ie.
of_node_add() becomes __of_attach_node_sysfs()) and all of them now
defer if of_init hasn't been called yet.

Callers of the new functions must hold the of_mutex to ensure there are
no race conditions with of_init(). The mutex ensures that there will
only ever be one writer to the tree at any given time. There can still
be any number of readers and the raw_spin_lock is still used to make
sure access to the data structure is still consistent.

Finally, put the function prototypes into of_private.h so they are
accessible to the transaction code.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[grant.likely: Changed suffix from _post to _sysfs to match existing code]
[grant.likely: Reorganized to eliminate trivial wrappers]
Signed-off-by: Grant Likely <grant.likely@linaro.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index 75fcc66fcefd..c875787fa394 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -41,11 +41,13 @@ void of_node_put(struct device_node *node)
 }
 EXPORT_SYMBOL(of_node_put);
 
-static void of_node_remove(struct device_node *np)
+void __of_detach_node_sysfs(struct device_node *np)
 {
 	struct property *pp;
 
 	BUG_ON(!of_node_is_initialized(np));
+	if (!of_kset)
+		return;
 
 	/* only remove properties if on sysfs */
 	if (of_node_is_attached(np)) {
@@ -115,11 +117,13 @@ int of_attach_node(struct device_node *np)
 	if (rc)
 		return rc;
 
+	mutex_lock(&of_mutex);
 	raw_spin_lock_irqsave(&devtree_lock, flags);
 	__of_attach_node(np);
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 
-	of_node_add(np);
+	__of_attach_node_sysfs(np);
+	mutex_unlock(&of_mutex);
 	return 0;
 }
 
@@ -174,11 +178,13 @@ int of_detach_node(struct device_node *np)
 	if (rc)
 		return rc;
 
+	mutex_lock(&of_mutex);
 	raw_spin_lock_irqsave(&devtree_lock, flags);
 	__of_detach_node(np);
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
 
-	of_node_remove(np);
+	__of_detach_node_sysfs(np);
+	mutex_unlock(&of_mutex);
 	return rc;
 }