[PATCH 5.15.y] device property: Make modifications of fwnode "flags" thread safe

[Douglas Anderson <dianders@chromium.org>]

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>
(cherry picked from commit f72e77c33e4b5657af35125e75bab249256030f3)
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
 drivers/base/core.c        | 12 ++++++------
 drivers/net/phy/mdio_bus.c |  4 ++--
 drivers/of/property.c      |  2 +-
 include/linux/fwnode.h     | 40 +++++++++++++++++++++++++++++---------
 4 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4fc62624a95e..31b47d812fa5 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -171,7 +171,7 @@ void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
 	if (fwnode->dev)
 		return;
 
-	fwnode->flags |= FWNODE_FLAG_NOT_DEVICE;
+	fwnode_set_flag(fwnode, FWNODE_FLAG_NOT_DEVICE);
 	fwnode_links_purge_consumers(fwnode);
 
 	fwnode_for_each_available_child_node(fwnode, child)
@@ -1620,11 +1620,11 @@ bool fw_devlink_is_strict(void)
 
 static void fw_devlink_parse_fwnode(struct fwnode_handle *fwnode)
 {
-	if (fwnode->flags & FWNODE_FLAG_LINKS_ADDED)
+	if (fwnode_test_flag(fwnode, FWNODE_FLAG_LINKS_ADDED))
 		return;
 
 	fwnode_call_int_op(fwnode, add_links);
-	fwnode->flags |= FWNODE_FLAG_LINKS_ADDED;
+	fwnode_set_flag(fwnode, FWNODE_FLAG_LINKS_ADDED);
 }
 
 static void fw_devlink_parse_fwtree(struct fwnode_handle *fwnode)
@@ -1765,7 +1765,7 @@ static int fw_devlink_create_devlink(struct device *con,
 	 * When such a flag is set, we can't create device links where P is the
 	 * supplier of C as that would delay the probe of C.
 	 */
-	if (sup_handle->flags & FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD &&
+	if (fwnode_test_flag(sup_handle, FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD) &&
 	    fwnode_is_ancestor_of(sup_handle, con->fwnode))
 		return -EINVAL;
 
@@ -1777,7 +1777,7 @@ static int fw_devlink_create_devlink(struct device *con,
 		 * supplier device indefinitely.
 		 */
 		if (sup_dev->links.status == DL_DEV_NO_DRIVER &&
-		    sup_handle->flags & FWNODE_FLAG_INITIALIZED) {
+		    fwnode_test_flag(sup_handle, FWNODE_FLAG_INITIALIZED)) {
 			ret = -EINVAL;
 			goto out;
 		}
@@ -1802,7 +1802,7 @@ static int fw_devlink_create_devlink(struct device *con,
 	}
 
 	/* Supplier that's already initialized without a struct device. */
-	if (sup_handle->flags & FWNODE_FLAG_INITIALIZED)
+	if (fwnode_test_flag(sup_handle, FWNODE_FLAG_INITIALIZED))
 		return -EINVAL;
 
 	/*
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index a8a4cd68f688..1c60581b46d1 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -534,8 +534,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 		return -EINVAL;
 
 	if (bus->parent && bus->parent->of_node)
-		bus->parent->of_node->fwnode.flags |=
-					FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD;
+		fwnode_set_flag(&bus->parent->of_node->fwnode,
+				FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD);
 
 	BUG_ON(bus->state != MDIOBUS_ALLOCATED &&
 	       bus->state != MDIOBUS_UNREGISTERED);
diff --git a/drivers/of/property.c b/drivers/of/property.c
index 905ac6466a5b..922f70aa46f3 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1130,7 +1130,7 @@ static int of_link_to_phandle(struct device_node *con_np,
 	sup_dev = get_dev_from_fwnode(&sup_np->fwnode);
 	if (!sup_dev &&
 	    (of_node_check_flag(sup_np, OF_POPULATED) ||
-	     sup_np->fwnode.flags & FWNODE_FLAG_NOT_DEVICE)) {
+	     fwnode_test_flag(&sup_np->fwnode, FWNODE_FLAG_NOT_DEVICE))) {
 		pr_debug("Not linking %pOFP to %pOFP - No struct device\n",
 			 con_np, sup_np);
 		of_node_put(sup_np);
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index f0833bafe6bd..022d9795269e 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/list.h>
+#include <linux/bitops.h>
 #include <linux/err.h>
 
 struct fwnode_operations;
@@ -27,10 +28,10 @@ struct device;
  *			     their respective drivers as soon as they are
  *			     added.
  */
-#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_LINKS_ADDED			0
+#define FWNODE_FLAG_NOT_DEVICE			1
+#define FWNODE_FLAG_INITIALIZED			2
+#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD	3
 
 struct fwnode_handle {
 	struct fwnode_handle *secondary;
@@ -38,7 +39,7 @@ struct fwnode_handle {
 	struct device *dev;
 	struct list_head suppliers;
 	struct list_head consumers;
-	u8 flags;
+	unsigned long flags;
 };
 
 struct fwnode_link {
@@ -176,16 +177,37 @@ 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);
 }
 
 extern u32 fw_devlink_get_flags(void);
-- 
2.54.0.545.g6539524ca2-goog