linux-kernel - [PATCH v1 1/1] device property: Allow error pointer for fwnode_handle

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Date:   Thu,  3 Mar 2022 17:06:10 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Nuno Sá <nuno.sa@...log.com>
Subject: [PATCH v1 1/1] device property: Allow error pointer for fwnode_handle_{get,put}()

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_OR_NULL(fwnode))
		...error handling...

Nevertheless the resulting fwnode may have bumped 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 error pointer for fwnode_handle_get() and
fwnode_handle_put().

Fixes: 83b34afb6b79 ("device property: Introduce fwnode_find_reference()")
Reported-by: Nuno Sá <nuno.sa@...log.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/base/property.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 2d70392fc982..df7b8c7ad264 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -776,7 +776,7 @@ EXPORT_SYMBOL_GPL(device_get_named_child_node);
  */
 struct fwnode_handle *fwnode_handle_get(struct fwnode_handle *fwnode)
 {
-	if (!fwnode_has_op(fwnode, get))
+	if (IS_ERR(fwnode) || !fwnode_has_op(fwnode, get))
 		return fwnode;
 
 	return fwnode_call_ptr_op(fwnode, get);
@@ -793,6 +793,9 @@ EXPORT_SYMBOL_GPL(fwnode_handle_get);
  */
 void fwnode_handle_put(struct fwnode_handle *fwnode)
 {
+	if (IS_ERR(fwnode) || !fwnode_has_op(fwnode, put))
+		return;
+
 	fwnode_call_void_op(fwnode, put);
 }
 EXPORT_SYMBOL_GPL(fwnode_handle_put);
-- 
2.34.1