net: phy: don't abuse devres in devm_mdiobus_register()

We currently have two managed helpers for mdiobus - devm_mdiobus_alloc()
and devm_mdiobus_register(). The idea behind devres is that the release
callback releases whatever resource the devm function allocates. In the
mdiobus case however there's no devres associated with the device by
devm_mdiobus_register(). Instead the release callback for
devm_mdiobus_alloc(): _devm_mdiobus_free() unregisters the device if
it is marked as managed.

This all seems wrong. The managed structure shouldn't need to know or
care about whether it's managed or not - and this is the case now for
struct mii_bus. The devres wrapper should be opaque to the managed
resource.

This changeset makes devm_mdiobus_alloc() and devm_mdiobus_register()
conform to common devres standards: devm_mdiobus_alloc() allocates a
devres structure and registers a callback that will call mdiobus_free().
__devm_mdiobus_register() allocated another devres and registers a
callback that will unregister the bus.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/driver-api/driver-model/devres.rst

@@ -342,7 +342,6 @@ LED
 MDIO
   devm_mdiobus_alloc()
   devm_mdiobus_alloc_size()
-  devm_mdiobus_free()
   devm_mdiobus_register()
 
 MEM

drivers/net/ethernet/realtek/r8169_main.c

@@ -5012,7 +5012,7 @@ static int r8169_mdio_register(struct rtl8169_private *tp)
 	new_bus->read = r8169_mdio_read_reg;
 	new_bus->write = r8169_mdio_write_reg;
 
-	ret = devm_mdiobus_register(new_bus);
+	ret = devm_mdiobus_register(&pdev->dev, new_bus);
 	if (ret)
 		return ret;
 

drivers/net/phy/mdio_bus.c

@@ -165,79 +165,6 @@ struct mii_bus *mdiobus_alloc_size(size_t size)
 }
 EXPORT_SYMBOL(mdiobus_alloc_size);
 
-static void _devm_mdiobus_free(struct device *dev, void *res)
-{
-	struct mii_bus *bus = *(struct mii_bus **)res;
-
-	if (bus->is_managed_registered && bus->state == MDIOBUS_REGISTERED)
-		mdiobus_unregister(bus);
-
-	mdiobus_free(bus);
-}
-
-static int devm_mdiobus_match(struct device *dev, void *res, void *data)
-{
-	struct mii_bus **r = res;
-
-	if (WARN_ON(!r || !*r))
-		return 0;
-
-	return *r == data;
-}
-
-/**
- * devm_mdiobus_alloc_size - Resource-managed mdiobus_alloc_size()
- * @dev:		Device to allocate mii_bus for
- * @sizeof_priv:	Space to allocate for private structure.
- *
- * Managed mdiobus_alloc_size. mii_bus allocated with this function is
- * automatically freed on driver detach.
- *
- * If an mii_bus allocated with this function needs to be freed separately,
- * devm_mdiobus_free() must be used.
- *
- * RETURNS:
- * Pointer to allocated mii_bus on success, NULL on failure.
- */
-struct mii_bus *devm_mdiobus_alloc_size(struct device *dev, int sizeof_priv)
-{
-	struct mii_bus **ptr, *bus;
-
-	ptr = devres_alloc(_devm_mdiobus_free, sizeof(*ptr), GFP_KERNEL);
-	if (!ptr)
-		return NULL;
-
-	/* use raw alloc_dr for kmalloc caller tracing */
-	bus = mdiobus_alloc_size(sizeof_priv);
-	if (bus) {
-		*ptr = bus;
-		devres_add(dev, ptr);
-		bus->is_managed = 1;
-	} else {
-		devres_free(ptr);
-	}
-
-	return bus;
-}
-EXPORT_SYMBOL_GPL(devm_mdiobus_alloc_size);
-
-/**
- * devm_mdiobus_free - Resource-managed mdiobus_free()
- * @dev:		Device this mii_bus belongs to
- * @bus:		the mii_bus associated with the device
- *
- * Free mii_bus allocated with devm_mdiobus_alloc_size().
- */
-void devm_mdiobus_free(struct device *dev, struct mii_bus *bus)
-{
-	int rc;
-
-	rc = devres_release(dev, _devm_mdiobus_free,
-			    devm_mdiobus_match, bus);
-	WARN_ON(rc);
-}
-EXPORT_SYMBOL_GPL(devm_mdiobus_free);
-
 /**
  * mdiobus_release - mii_bus device release callback
  * @d: the target struct device that contains the mii_bus

drivers/net/phy/mdio_devres.c

 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <linux/device.h>
 #include <linux/phy.h>
+#include <linux/stddef.h>
+
+struct mdiobus_devres {
+	struct mii_bus *mii;
+};
+
+static void devm_mdiobus_free(struct device *dev, void *this)
+{
+	struct mdiobus_devres *dr = this;
+
+	mdiobus_free(dr->mii);
+}
+
+/**
+ * devm_mdiobus_alloc_size - Resource-managed mdiobus_alloc_size()
+ * @dev:		Device to allocate mii_bus for
+ * @sizeof_priv:	Space to allocate for private structure
+ *
+ * Managed mdiobus_alloc_size. mii_bus allocated with this function is
+ * automatically freed on driver detach.
+ *
+ * RETURNS:
+ * Pointer to allocated mii_bus on success, NULL on out-of-memory error.
+ */
+struct mii_bus *devm_mdiobus_alloc_size(struct device *dev, int sizeof_priv)
+{
+	struct mdiobus_devres *dr;
+
+	dr = devres_alloc(devm_mdiobus_free, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return NULL;
+
+	dr->mii = mdiobus_alloc_size(sizeof_priv);
+	if (!dr->mii) {
+		devres_free(dr);
+		return NULL;
+	}
+
+	devres_add(dev, dr);
+	return dr->mii;
+}
+EXPORT_SYMBOL(devm_mdiobus_alloc_size);
+
+static void devm_mdiobus_unregister(struct device *dev, void *this)
+{
+	struct mdiobus_devres *dr = this;
+
+	mdiobus_unregister(dr->mii);
+}
+
+static int mdiobus_devres_match(struct device *dev,
+				void *this, void *match_data)
+{
+	struct mdiobus_devres *res = this;
+	struct mii_bus *mii = match_data;
+
+	return mii == res->mii;
+}
 
 /**
  * __devm_mdiobus_register - Resource-managed variant of mdiobus_register()
+ * @dev:	Device to register mii_bus for
  * @bus:	MII bus structure to register
  * @owner:	Owning module
  *
  * Returns 0 on success, negative error number on failure.
  */
-int __devm_mdiobus_register(struct mii_bus *bus, struct module *owner)
+int __devm_mdiobus_register(struct device *dev, struct mii_bus *bus,
+			    struct module *owner)
 {
+	struct mdiobus_devres *dr;
 	int ret;
 
-	if (!bus->is_managed)
-		return -EPERM;
+	if (WARN_ON(!devres_find(dev, devm_mdiobus_free,
+				 mdiobus_devres_match, bus)))
+		return -EINVAL;
 
-	ret = __mdiobus_register(bus, owner);
-	if (!ret)
-		bus->is_managed_registered = 1;
+	dr = devres_alloc(devm_mdiobus_unregister, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
 
+	ret = __mdiobus_register(bus, owner);
+	if (ret) {
+		devres_free(dr);
 		return ret;
+	}
+
+	dr->mii = bus;
+	devres_add(dev, dr);
+	return 0;
 }
 EXPORT_SYMBOL(__devm_mdiobus_register);

include/linux/phy.h

@@ -261,9 +261,6 @@ struct mii_bus {
 	int (*reset)(struct mii_bus *bus);
 	struct mdio_bus_stats stats[PHY_MAX_ADDR];
 
-	unsigned int is_managed:1;	/* is device-managed */
-	unsigned int is_managed_registered:1;
-
 	/*
 	 * A lock to ensure that only one thing can read/write
 	 * the MDIO bus at a time
@@ -322,9 +319,11 @@ static inline struct mii_bus *mdiobus_alloc(void)
 }
 
 int __mdiobus_register(struct mii_bus *bus, struct module *owner);
-int __devm_mdiobus_register(struct mii_bus *bus, struct module *owner);
+int __devm_mdiobus_register(struct device *dev, struct mii_bus *bus,
+			    struct module *owner);
 #define mdiobus_register(bus) __mdiobus_register(bus, THIS_MODULE)
-#define devm_mdiobus_register(bus) __devm_mdiobus_register(bus, THIS_MODULE)
+#define devm_mdiobus_register(dev, bus) \
+		__devm_mdiobus_register(dev, bus, THIS_MODULE)
 
 void mdiobus_unregister(struct mii_bus *bus);
 void mdiobus_free(struct mii_bus *bus);
@@ -335,7 +334,6 @@ static inline struct mii_bus *devm_mdiobus_alloc(struct device *dev)
 }
 
 struct mii_bus *mdio_find_bus(const char *mdio_name);
-void devm_mdiobus_free(struct device *dev, struct mii_bus *bus);
 struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr);
 
 #define PHY_INTERRUPT_DISABLED	false