device property: Make modifications of fwnode "flags" thread safe

In various places in the kernel, we modify the fwnode "flags" member
by doing either:
  fwnode->flags |= SOME_FLAG;
  fwnode->flags &= ~SOME_FLAG;

This type of modification is not thread-safe. If two threads are both
mucking with the flags at the same time then one can clobber the
other.

While flags are often modified while under the "fwnode_link_lock",
this is not universally true.

Create some accessor functions for setting, clearing, and testing the
FWNODE flags and move all users to these accessor functions. New
accessor functions use set_bit() and clear_bit(), which are
thread-safe.

Cc: stable@vger.kernel.org
Fixes: c2c724c868c4 ("driver core: Add fw_devlink_parse_fwtree()")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Reviewed-by: Saravana Kannan <saravanak@kernel.org>
Link: https://patch.msgid.link/20260317090112.v2.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid
[ Fix fwnode_clear_flag() argument alignment, restore dropped blank
  line in fwnode_dev_initialized(), and remove unnecessary parentheses
  around fwnode_test_flag() calls. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 33 insertions, 11 deletions

diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index 097be89487bf..80b38fbf2121 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -15,6 +15,7 @@
 #define _LINUX_FWNODE_H_
 
 #include <linux/bits.h>
+#include <linux/bitops.h>
 #include <linux/err.h>
 #include <linux/list.h>
 #include <linux/types.h>
@@ -42,12 +43,12 @@ struct device;
  *		suppliers. Only enforce ordering with suppliers that have
  *		drivers.
  */
-#define FWNODE_FLAG_LINKS_ADDED			BIT(0)
-#define FWNODE_FLAG_NOT_DEVICE			BIT(1)
-#define FWNODE_FLAG_INITIALIZED			BIT(2)
-#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD	BIT(3)
-#define FWNODE_FLAG_BEST_EFFORT			BIT(4)
-#define FWNODE_FLAG_VISITED			BIT(5)
+#define FWNODE_FLAG_LINKS_ADDED			0
+#define FWNODE_FLAG_NOT_DEVICE			1
+#define FWNODE_FLAG_INITIALIZED			2
+#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD	3
+#define FWNODE_FLAG_BEST_EFFORT			4
+#define FWNODE_FLAG_VISITED			5
 
 struct fwnode_handle {
 	struct fwnode_handle *secondary;
@@ -57,7 +58,7 @@ struct fwnode_handle {
 	struct device *dev;
 	struct list_head suppliers;
 	struct list_head consumers;
-	u8 flags;
+	unsigned long flags;
 };
 
 /*
@@ -212,16 +213,37 @@ static inline void fwnode_init(struct fwnode_handle *fwnode,
 	INIT_LIST_HEAD(&fwnode->suppliers);
 }
 
+static inline void fwnode_set_flag(struct fwnode_handle *fwnode,
+				   unsigned int bit)
+{
+	set_bit(bit, &fwnode->flags);
+}
+
+static inline void fwnode_clear_flag(struct fwnode_handle *fwnode,
+				     unsigned int bit)
+{
+	clear_bit(bit, &fwnode->flags);
+}
+
+static inline void fwnode_assign_flag(struct fwnode_handle *fwnode,
+				      unsigned int bit, bool value)
+{
+	assign_bit(bit, &fwnode->flags, value);
+}
+
+static inline bool fwnode_test_flag(struct fwnode_handle *fwnode,
+				    unsigned int bit)
+{
+	return test_bit(bit, &fwnode->flags);
+}
+
 static inline void fwnode_dev_initialized(struct fwnode_handle *fwnode,
 					  bool initialized)
 {
 	if (IS_ERR_OR_NULL(fwnode))
 		return;
 
-	if (initialized)
-		fwnode->flags |= FWNODE_FLAG_INITIALIZED;
-	else
-		fwnode->flags &= ~FWNODE_FLAG_INITIALIZED;
+	fwnode_assign_flag(fwnode, FWNODE_FLAG_INITIALIZED, initialized);
 }
 
 int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup,