netdev - [PATCH v2 2/2] net: phy: Ensure the MDIO bus module is held

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Date:	Wed, 23 Jul 2014 16:47:32 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	<netdev@...r.kernel.org>
Cc:	David Miller <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Subject: [PATCH v2 2/2] net: phy: Ensure the MDIO bus module is held

This commit adds proper module_{get,put} to prevent the MDIO bus module
from being unloaded while the phydev is connected. By doing so, we fix
a kernel panic produced when a MDIO driver is removed, but the phydev
that relies on it is attached and running.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
---
 drivers/net/phy/phy_device.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 4f4568e..1a5815c 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -575,6 +575,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		      u32 flags, phy_interface_t interface)
 {
 	struct device *d = &phydev->dev;
+	struct module *bus_module;
 	int err;
 
 	/* Assume that if there is no driver, that it doesn't
@@ -599,6 +600,14 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		return -EBUSY;
 	}
 
+	/* Increment the bus module reference count */
+	bus_module = phydev->bus->dev.driver ?
+		     phydev->bus->dev.driver->owner : NULL;
+	if (!try_module_get(bus_module)) {
+		dev_err(&dev->dev, "failed to get the bus module\n");
+		return -EIO;
+	}
+
 	phydev->attached_dev = dev;
 	dev->phydev = phydev;
 
@@ -664,6 +673,10 @@ EXPORT_SYMBOL(phy_attach);
 void phy_detach(struct phy_device *phydev)
 {
 	int i;
+
+	if (phydev->bus->dev.driver)
+		module_put(phydev->bus->dev.driver->owner);
+
 	phydev->attached_dev->phydev = NULL;
 	phydev->attached_dev = NULL;
 	phy_suspend(phydev);
-- 
2.0.1

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