[PATCH v2 07/10] net: phy: don't abuse devres in devm_mdiobus_register()

Bartosz Golaszewski
2020-06-29T20:59:59Z

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>
---
.../driver-api/driver-model/devres.rst | 1 -
drivers/net/ethernet/realtek/r8169_main.c | 2 +-
drivers/net/phy/mdio_bus.c | 73 ----------------
drivers/net/phy/mdio_devres.c | 83 +++++++++++++++++--
include/linux/phy.h | 10 +--
5 files changed, 82 insertions(+), 87 deletions(-)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 5463fc8a60c1..e0333d66a7f4 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/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
diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index b660ddbe4025..bfb68a1b1958 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5103,7 +5103,7 @@ 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;

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 6ceee82b2839..42192991f55d 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/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
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);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 4935867f024b..3695e9d6b3f6 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -260,9 +260,6 @@ 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
@@ -313,9 +310,11 @@ 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);
@@ -326,7 +325,6 @@ 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
--
2.26.1