[PATCH v6 1/5] device property: Allow error pointer to be passed to fwnode APIs

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

Some of the fwnode APIs might return an error pointer instead of NULL
or valid fwnode handle. The result of such API call may be considered
optional and hence the test for it is usually done in a form of

	fwnode = fwnode_find_reference(...);
	if (IS_ERR(fwnode))
		...error handling...

Nevertheless the resulting fwnode may have bumped the reference count
and hence caller of the above API is obliged to call fwnode_handle_put().
Since fwnode may be not valid either as NULL or error pointer the check
has to be performed there. This approach uglifies the code and adds
a point of making a mistake, i.e. forgetting about error point case.

To prevent this, allow an error pointer to be passed to the fwnode APIs.

Fixes: 83b34afb6b79 ("device property: Introduce fwnode_find_reference()")
Reported-by: Nuno Sá <nuno.sa@analog.com>
Tested-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Michael Walle <michael@walle.cc>
---
v6: added tag (Michael), avoid shadowing error code (Michael)
 drivers/base/property.c | 89 +++++++++++++++++++++++------------------
 include/linux/fwnode.h  | 10 ++---
 2 files changed, 56 insertions(+), 43 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 3560c4419d11..6ecc1398b0ba 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -47,12 +47,14 @@ bool fwnode_property_present(const struct fwnode_handle *fwnode,
 {
 	bool ret;
 
+	if (IS_ERR_OR_NULL(fwnode))
+		return false;
+
 	ret = fwnode_call_bool_op(fwnode, property_present, propname);
-	if (ret == false && !IS_ERR_OR_NULL(fwnode) &&
-	    !IS_ERR_OR_NULL(fwnode->secondary))
-		ret = fwnode_call_bool_op(fwnode->secondary, property_present,
-					 propname);
-	return ret;
+	if (ret)
+		return ret;
+
+	return fwnode_call_bool_op(fwnode->secondary, property_present, propname);
 }
 EXPORT_SYMBOL_GPL(fwnode_property_present);
 
@@ -232,15 +234,16 @@ static int fwnode_property_read_int_array(const struct fwnode_handle *fwnode,
 {
 	int ret;
 
+	if (IS_ERR_OR_NULL(fwnode))
+		return -EINVAL;
+
 	ret = fwnode_call_int_op(fwnode, property_read_int_array, propname,
 				 elem_size, val, nval);
-	if (ret == -EINVAL && !IS_ERR_OR_NULL(fwnode) &&
-	    !IS_ERR_OR_NULL(fwnode->secondary))
-		ret = fwnode_call_int_op(
-			fwnode->secondary, property_read_int_array, propname,
-			elem_size, val, nval);
+	if (ret != -EINVAL)
+		return ret;
 
-	return ret;
+	return fwnode_call_int_op(fwnode->secondary, property_read_int_array, propname,
+				  elem_size, val, nval);
 }
 
 /**
@@ -371,14 +374,16 @@ int fwnode_property_read_string_array(const struct fwnode_handle *fwnode,
 {
 	int ret;
 
+	if (IS_ERR_OR_NULL(fwnode))
+		return -EINVAL;
+
 	ret = fwnode_call_int_op(fwnode, property_read_string_array, propname,
 				 val, nval);
-	if (ret == -EINVAL && !IS_ERR_OR_NULL(fwnode) &&
-	    !IS_ERR_OR_NULL(fwnode->secondary))
-		ret = fwnode_call_int_op(fwnode->secondary,
-					 property_read_string_array, propname,
-					 val, nval);
-	return ret;
+	if (ret != -EINVAL)
+		return ret;
+
+	return fwnode_call_int_op(fwnode->secondary, property_read_string_array, propname,
+				  val, nval);
 }
 EXPORT_SYMBOL_GPL(fwnode_property_read_string_array);
 
@@ -480,15 +485,19 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 {
 	int ret;
 
+	if (IS_ERR_OR_NULL(fwnode))
+		return -ENOENT;
+
 	ret = fwnode_call_int_op(fwnode, get_reference_args, prop, nargs_prop,
 				 nargs, index, args);
+	if (ret == 0)
+		return ret;
 
-	if (ret < 0 && !IS_ERR_OR_NULL(fwnode) &&
-	    !IS_ERR_OR_NULL(fwnode->secondary))
-		ret = fwnode_call_int_op(fwnode->secondary, get_reference_args,
-					 prop, nargs_prop, nargs, index, args);
+	if (IS_ERR_OR_NULL(fwnode->secondary))
+		return ret;
 
-	return ret;
+	return fwnode_call_int_op(fwnode->secondary, get_reference_args, prop, nargs_prop,
+				  nargs, index, args);
 }
 EXPORT_SYMBOL_GPL(fwnode_property_get_reference_args);
 
@@ -635,12 +644,13 @@ EXPORT_SYMBOL_GPL(fwnode_count_parents);
 struct fwnode_handle *fwnode_get_nth_parent(struct fwnode_handle *fwnode,
 					    unsigned int depth)
 {
-	unsigned int i;
-
 	fwnode_handle_get(fwnode);
 
-	for (i = 0; i < depth && fwnode; i++)
+	do {
+		if (depth-- == 0)
+			break;
 		fwnode = fwnode_get_next_parent(fwnode);
+	} while (fwnode);
 
 	return fwnode;
 }
@@ -659,17 +669,17 @@ EXPORT_SYMBOL_GPL(fwnode_get_nth_parent);
 bool fwnode_is_ancestor_of(struct fwnode_handle *test_ancestor,
 				  struct fwnode_handle *test_child)
 {
-	if (!test_ancestor)
+	if (IS_ERR_OR_NULL(test_ancestor))
 		return false;
 
 	fwnode_handle_get(test_child);
-	while (test_child) {
+	do {
 		if (test_child == test_ancestor) {
 			fwnode_handle_put(test_child);
 			return true;
 		}
 		test_child = fwnode_get_next_parent(test_child);
-	}
+	} while (test_child);
 	return false;
 }
 
@@ -698,7 +708,7 @@ fwnode_get_next_available_child_node(const struct fwnode_handle *fwnode,
 {
 	struct fwnode_handle *next_child = child;
 
-	if (!fwnode)
+	if (IS_ERR_OR_NULL(fwnode))
 		return NULL;
 
 	do {
@@ -722,16 +732,16 @@ struct fwnode_handle *device_get_next_child_node(struct device *dev,
 	const struct fwnode_handle *fwnode = dev_fwnode(dev);
 	struct fwnode_handle *next;
 
+	if (IS_ERR_OR_NULL(fwnode))
+		return NULL;
+
 	/* Try to find a child in primary fwnode */
 	next = fwnode_get_next_child_node(fwnode, child);
 	if (next)
 		return next;
 
 	/* When no more children in primary, continue with secondary */
-	if (fwnode && !IS_ERR_OR_NULL(fwnode->secondary))
-		next = fwnode_get_next_child_node(fwnode->secondary, child);
-
-	return next;
+	return fwnode_get_next_child_node(fwnode->secondary, child);
 }
 EXPORT_SYMBOL_GPL(device_get_next_child_node);
 
@@ -798,6 +808,9 @@ EXPORT_SYMBOL_GPL(fwnode_handle_put);
  */
 bool fwnode_device_is_available(const struct fwnode_handle *fwnode)
 {
+	if (IS_ERR_OR_NULL(fwnode))
+		return false;
+
 	if (!fwnode_has_op(fwnode, device_is_available))
 		return true;
 
@@ -958,14 +971,14 @@ fwnode_graph_get_next_endpoint(const struct fwnode_handle *fwnode,
 		parent = fwnode_graph_get_port_parent(prev);
 	else
 		parent = fwnode;
+	if (IS_ERR_OR_NULL(parent))
+		return NULL;
 
 	ep = fwnode_call_ptr_op(parent, graph_get_next_endpoint, prev);
+	if (ep)
+		return ep;
 
-	if (IS_ERR_OR_NULL(ep) &&
-	    !IS_ERR_OR_NULL(parent) && !IS_ERR_OR_NULL(parent->secondary))
-		ep = fwnode_graph_get_next_endpoint(parent->secondary, NULL);
-
-	return ep;
+	return fwnode_graph_get_next_endpoint(parent->secondary, NULL);
 }
 EXPORT_SYMBOL_GPL(fwnode_graph_get_next_endpoint);
 
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index 6ab69871b06d..9a81c4410b9f 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -153,12 +153,12 @@ struct fwnode_operations {
 	int (*add_links)(struct fwnode_handle *fwnode);
 };
 
-#define fwnode_has_op(fwnode, op)				\
-	((fwnode) && (fwnode)->ops && (fwnode)->ops->op)
+#define fwnode_has_op(fwnode, op)					\
+	(!IS_ERR_OR_NULL(fwnode) && (fwnode)->ops && (fwnode)->ops->op)
+
 #define fwnode_call_int_op(fwnode, op, ...)				\
-	(fwnode ? (fwnode_has_op(fwnode, op) ?				\
-		   (fwnode)->ops->op(fwnode, ## __VA_ARGS__) : -ENXIO) : \
-	 -EINVAL)
+	(fwnode_has_op(fwnode, op) ?					\
+	 (fwnode)->ops->op(fwnode, ## __VA_ARGS__) : (IS_ERR_OR_NULL(fwnode) ? -EINVAL : -ENXIO))
 
 #define fwnode_call_bool_op(fwnode, op, ...)		\
 	(fwnode_has_op(fwnode, op) ?			\
-- 
2.35.1