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>

1 files changed, 77 insertions, 6 deletions

diff --git a/drivers/net/phy/mdio_devres.c b/drivers/net/phy/mdio_devres.c
index 3ee887733d4a..0b9bd9a61378 100644
--- a/drivers/net/phy/mdio_devres.c
+++ b/drivers/net/phy/mdio_devres.c
@@ -1,25 +1,96 @@
 // 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;
+
+	dr = devres_alloc(devm_mdiobus_unregister, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
 
 	ret = __mdiobus_register(bus, owner);
-	if (!ret)
-		bus->is_managed_registered = 1;
+	if (ret) {
+		devres_free(dr);
+		return ret;
+	}
 
-	return ret;
+	dr->mii = bus;
+	devres_add(dev, dr);
+	return 0;
 }
 EXPORT_SYMBOL(__devm_mdiobus_register);