Subject: [PATCH 05/11] net: core: provide devm_register_netdev()

From: Bartosz Golaszewski <[email-masked]>
Date: Tue, 5 May 2020 16:02:25 +0200

From: Bartosz Golaszewski <[email-masked]>

Provide devm_register_netdev() - a device resource managed variant
of register_netdev(). This new helper will only work for net_device
structs that have a parent device assigned and are devres managed too.

Signed-off-by: Bartosz Golaszewski <[email-masked]>
---
 include/linux/netdevice.h |  4 ++++
 net/core/dev.c            | 48 +++++++++++++++++++++++++++++++++++++++
 net/ethernet/eth.c        |  1 +
 3 files changed, 53 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 130a668049ab..433bd5ca2efc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1515,6 +1515,8 @@ struct net_device_ops {
  * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device
  * @IFF_L3MDEV_RX_HANDLER: only invoke the rx handler of L3 master device
  * @IFF_LIVE_RENAME_OK: rename is allowed while device is up and running
+ * @IFF_IS_DEVRES: this structure was allocated dynamically and is managed by
+ *	devres
  */
 enum netdev_priv_flags {
 	IFF_802_1Q_VLAN			= 1<<0,
@@ -1548,6 +1550,7 @@ enum netdev_priv_flags {
 	IFF_FAILOVER_SLAVE		= 1<<28,
 	IFF_L3MDEV_RX_HANDLER		= 1<<29,
 	IFF_LIVE_RENAME_OK		= 1<<30,
+	IFF_IS_DEVRES			= 1<<31,
 };
 
 #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
@@ -4206,6 +4209,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 			 count)
 
 int register_netdev(struct net_device *dev);
+int devm_register_netdev(struct net_device *ndev);
 void unregister_netdev(struct net_device *dev);
 
 /* General hardware address lists handling functions */
diff --git a/net/core/dev.c b/net/core/dev.c
index 522288177bbd..99db537c9468 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9519,6 +9519,54 @@ int register_netdev(struct net_device *dev)
 }
 EXPORT_SYMBOL(register_netdev);
 
+struct netdevice_devres {
+	struct net_device *ndev;
+};
+
+static void devm_netdev_release(struct device *dev, void *this)
+{
+	struct netdevice_devres *res = this;
+
+	unregister_netdev(res->ndev);
+}
+
+/**
+ *	devm_register_netdev - resource managed variant of register_netdev()
+ *	@ndev: device to register
+ *
+ *	This is a devres variant of register_netdev() for which the unregister
+ *	function will be call automatically when the parent device of ndev
+ *	is detached.
+ */
+int devm_register_netdev(struct net_device *ndev)
+{
+	struct netdevice_devres *dr;
+	int ret;
+
+	/* struct net_device itself must be devres managed. */
+	BUG_ON(!(ndev->priv_flags & IFF_IS_DEVRES));
+	/* struct net_device must have a parent device - it will be the device
+	 * managing this resource.
+	 */
+	BUG_ON(!ndev->dev.parent);
+
+	dr = devres_alloc(devm_netdev_release, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	ret = register_netdev(ndev);
+	if (ret) {
+		devres_free(dr);
+		return ret;
+	}
+
+	dr->ndev = ndev;
+	devres_add(ndev->dev.parent, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_register_netdev);
+
 int netdev_refcnt_read(const struct net_device *dev)
 {
 	int i, refcnt = 0;
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index c8b903302ff2..ce9b5e576f20 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -423,6 +423,7 @@ struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
 
 	*dr = netdev;
 	devres_add(dev, dr);
+	netdev->priv_flags |= IFF_IS_DEVRES;
 
 	return netdev;
 }
-- 
2.25.0