Subject: [PATCH v2 05/14] net: core: provide priv_to_netdev()

From: Bartosz Golaszewski <[email-masked]>
Date: Mon, 11 May 2020 17:07:50 +0200

From: Bartosz Golaszewski <[email-masked]>

Appropriate amount of extra memory for private data is allocated at
the end of struct net_device. We have a helper - netdev_priv() - that
returns its address but we don't have the reverse: a function which
given the address of the private data, returns the address of struct
net_device.

This has caused many drivers to store the pointer to net_device in
the private data structure, which basically means storing the pointer
to a structure in this very structure.

This patch proposes to add priv_to_netdev() - a helper which converts
the address of the private data to the address of the associated
net_device.

Signed-off-by: Bartosz Golaszewski <[email-masked]>
---
 include/linux/netdevice.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 130a668049ab..933c6808a87f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2249,6 +2249,18 @@ static inline void *netdev_priv(const struct net_device *dev)
 	return (char *)dev + ALIGN(sizeof(struct net_device), NETDEV_ALIGN);
 }
 
+/**
+ *	priv_to_netdev - get the net_device from private data
+ *	@priv: net_device private data
+ *
+ * Get the address of network device associated with this private data.
+ */
+static inline struct net_device *priv_to_netdev(void *priv)
+{
+	priv = (char *)priv - ALIGN(sizeof(struct net_device), NETDEV_ALIGN);
+	return (struct net_device *)priv;
+}
+
 /* Set the sysfs physical device reference for the network logical device
  * if set prior to registration will cause a symlink during initialization.
  */
-- 
2.25.0