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[PATCH 5/9] of_mdio: fix MDIO phy device refcounting

From Russell King <rmk+kernel@arm.linux.org.uk>
Newsgroups linux.kernel
Subject [PATCH 5/9] of_mdio: fix MDIO phy device refcounting
Date 2015-09-22 18:20 +0200
Message-ID <qbysq-219-21@gated-at.bofh.it> (permalink)
References <qbysp-219-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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bus_find_device() is defined as:

 * This is similar to the bus_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.

and it does indeed return a reference-counted pointer to the device:

        while ((dev = next_device(&i)))
                if (match(dev, data) && get_device(dev))
                                        ^^^^^^^^^^^^^^^
                        break;
        klist_iter_exit(&i);
        return dev;

What that means is that when we're done with the struct device, we must
drop that reference.  Neither of_phy_connect() nor of_phy_attach() did
this when phy_connect_direct() or phy_attach_direct() failed.

With our previous patch, phy_connect_direct() and phy_attach_direct()
take a new refcount on the phy device when successful, so we can drop
our local reference immediatley after these functions, whether or not
they succeeded.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/of/of_mdio.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 1350fa25cdb0..a87a868fed64 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -197,7 +197,8 @@ static int of_phy_match(struct device *dev, void *phy_np)
  * of_phy_find_device - Give a PHY node, find the phy_device
  * @phy_np: Pointer to the phy's device tree node
  *
- * Returns a pointer to the phy_device.
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure.
  */
 struct phy_device *of_phy_find_device(struct device_node *phy_np)
 {
@@ -217,7 +218,9 @@ EXPORT_SYMBOL(of_phy_find_device);
  * @hndlr: Link state callback for the network device
  * @iface: PHY data interface type
  *
- * Returns a pointer to the phy_device if successful.  NULL otherwise
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped by calling phy_disconnect() or phy_detach().
  */
 struct phy_device *of_phy_connect(struct net_device *dev,
 				  struct device_node *phy_np,
@@ -225,13 +228,19 @@ struct phy_device *of_phy_connect(struct net_device *dev,
 				  phy_interface_t iface)
 {
 	struct phy_device *phy = of_phy_find_device(phy_np);
+	int ret;
 
 	if (!phy)
 		return NULL;
 
 	phy->dev_flags = flags;
 
-	return phy_connect_direct(dev, phy, hndlr, iface) ? NULL : phy;
+	ret = phy_connect_direct(dev, phy, hndlr, iface);
+
+	/* refcount is held by phy_connect_direct() on success */
+	put_device(&phy->dev);
+
+	return ret ? NULL : phy;
 }
 EXPORT_SYMBOL(of_phy_connect);
 
@@ -241,17 +250,27 @@ EXPORT_SYMBOL(of_phy_connect);
  * @phy_np: Node pointer for the PHY
  * @flags: flags to pass to the PHY
  * @iface: PHY data interface type
+ *
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped by calling phy_disconnect() or phy_detach().
  */
 struct phy_device *of_phy_attach(struct net_device *dev,
 				 struct device_node *phy_np, u32 flags,
 				 phy_interface_t iface)
 {
 	struct phy_device *phy = of_phy_find_device(phy_np);
+	int ret;
 
 	if (!phy)
 		return NULL;
 
-	return phy_attach_direct(dev, phy, flags, iface) ? NULL : phy;
+	ret = phy_attach_direct(dev, phy, flags, iface);
+
+	/* refcount is held by phy_attach_direct() on success */
+	put_device(&phy->dev);
+
+	return ret ? NULL : phy;
 }
 EXPORT_SYMBOL(of_phy_attach);
 
-- 
2.1.0

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Thread

[PATCH v2 0/9] Phy, mdiobus, and netdev struct device fixes Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 8/9] phy: add phy_device_remove() Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 5/9] of_mdio: fix MDIO phy device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 6/9] net: fix phy refcounting in a bunch of drivers Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 9/9] net: fix net_device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 2/9] net: dsa: fix of_mdio_find_bus() device refcount leak Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 3/9] phy: fix mdiobus module safety Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  [PATCH 4/9] phy: add proper phy struct device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-22 18:20 +0200
  Re: [PATCH v2 0/9] Phy, mdiobus, and netdev struct device fixes David Miller <davem@davemloft.net> - 2015-09-24 01:30 +0200
    Re: [PATCH v2 0/9] Phy, mdiobus, and netdev struct device fixes Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-24 18:10 +0200
  [PATCH RESEND v3 2/9] net: dsa: fix of_mdio_find_bus() device  refcount leak Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 7/9] phy: fixed-phy: properly validate phy in  fixed_phy_update_state() Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 5/9] of_mdio: fix MDIO phy device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
    Re: [PATCH RESEND v3 5/9] of_mdio: fix MDIO phy device refcounting Rob Herring <robh@kernel.org> - 2015-09-25 00:30 +0200
  [PATCH RESEND v3 4/9] phy: add proper phy struct device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 8/9] phy: add phy_device_remove() Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 1/9] phy: fix of_mdio_find_bus() device refcount  leak Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 6/9] net: fix phy refcounting in a bunch of drivers Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 3/9] phy: fix mdiobus module safety Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:40 +0200
  [PATCH RESEND v3 9/9] net: fix net_device refcounting Russell King <rmk+kernel@arm.linux.org.uk> - 2015-09-24 21:50 +0200

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