netdev - [PATCH v2 05/14] net: core: provide priv_to

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Date:   Mon, 11 May 2020 17:07:50 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Rob Herring <robh+dt@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Matthias Brugger <matthias.bgg@...il.com>,
        John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Fabien Parent <fparent@...libre.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Edwin Peer <edwin.peer@...adcom.com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Stephane Le Provost <stephane.leprovost@...iatek.com>,
        Pedro Tsai <pedro.tsai@...iatek.com>,
        Andrew Perepech <andrew.perepech@...iatek.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [PATCH v2 05/14] net: core: provide priv_to_netdev()

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

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 <bgolaszewski@...libre.com>
---
 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