[PATCH v2 0/5] net: provide a devres variant of register_netdev()

[PATCH v2 0/5] net: provide a devres variant of register_netdev()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Using devres helpers allows to shrink the probing code, avoid memory leaks in
error paths make sure the order in which resources are freed is the exact
opposite of their allocation. This series proposes to add a devres variant
of register_netdev() that will only work with net_device structures whose
memory is also managed.

First we add the missing documentation entry for the only other networking
devres helper: devm_alloc_etherdev().

Next we move devm_alloc_etherdev() into a separate source file.

We then use a proxy structure in devm_alloc_etherdev() to improve readability.

Last: we implement devm_register_netdev() and use it in mtk-eth-mac driver.

v1 -> v2:
- rebase on top of net-next after driver rename, no functional changes

Bartosz Golaszewski (5):
  Documentation: devres: add a missing section for networking helpers
  net: move devres helpers into a separate source file
  net: devres: define a separate devres structure for
    devm_alloc_etherdev()
  net: devres: provide devm_register_netdev()
  net: ethernet: mtk_star_emac: use devm_register_netdev()

 .../driver-api/driver-model/devres.rst        |  5 +
 drivers/net/ethernet/mediatek/mtk_star_emac.c | 17 +---
 include/linux/netdevice.h                     |  2 +
 net/Makefile                                  |  2 +-
 net/devres.c                                  | 95 +++++++++++++++++++
 net/ethernet/eth.c                            | 28 ------
 6 files changed, 104 insertions(+), 45 deletions(-)
 create mode 100644 net/devres.c

-- 
2.25.0

[PATCH v2 1/5] Documentation: devres: add a missing section for networking helpers

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Add a new section for networking devres helpers to devres.rst and list
the two existing devm functions.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 Documentation/driver-api/driver-model/devres.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 46c13780994c..50df28d20fa7 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -372,6 +372,10 @@ MUX
   devm_mux_chip_register()
   devm_mux_control_get()
 
+NET
+  devm_alloc_etherdev()
+  devm_alloc_etherdev_mqs()
+
 PER-CPU MEM
   devm_alloc_percpu()
   devm_free_percpu()
-- 
2.25.0

[PATCH v2 2/5] net: move devres helpers into a separate source file

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

There's currently only a single devres helper in net/ - devm variant
of alloc_etherdev. Let's move it to net/devres.c with the intention of
assing a second one: devm_register_netdev(). This new routine will need
to know the address of the release function of devm_alloc_etherdev() so
that it can verify (using devres_find()) that the struct net_device
that's being passed to it is also resource managed.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 net/Makefile       |  2 +-
 net/devres.c       | 36 ++++++++++++++++++++++++++++++++++++
 net/ethernet/eth.c | 28 ----------------------------
 3 files changed, 37 insertions(+), 29 deletions(-)
 create mode 100644 net/devres.c

diff --git a/net/Makefile b/net/Makefile
index 07ea48160874..5744bf1997fd 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -6,7 +6,7 @@
 # Rewritten to use lists instead of if-statements.
 #
 
-obj-$(CONFIG_NET)		:= socket.o core/
+obj-$(CONFIG_NET)		:= devres.o socket.o core/
 
 tmp-$(CONFIG_COMPAT) 		:= compat.o
 obj-$(CONFIG_NET)		+= $(tmp-y)
diff --git a/net/devres.c b/net/devres.c
new file mode 100644
index 000000000000..c1465d9f9019
--- /dev/null
+++ b/net/devres.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This file contains all networking devres helpers.
+ */
+
+#include <linux/device.h>
+#include <linux/etherdevice.h>
+#include <linux/netdevice.h>
+
+static void devm_free_netdev(struct device *dev, void *res)
+{
+	free_netdev(*(struct net_device **)res);
+}
+
+struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
+					   unsigned int txqs, unsigned int rxqs)
+{
+	struct net_device **dr;
+	struct net_device *netdev;
+
+	dr = devres_alloc(devm_free_netdev, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return NULL;
+
+	netdev = alloc_etherdev_mqs(sizeof_priv, txqs, rxqs);
+	if (!netdev) {
+		devres_free(dr);
+		return NULL;
+	}
+
+	*dr = netdev;
+	devres_add(dev, dr);
+
+	return netdev;
+}
+EXPORT_SYMBOL(devm_alloc_etherdev_mqs);
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index c8b903302ff2..dac65180c4ef 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -400,34 +400,6 @@ struct net_device *alloc_etherdev_mqs(int sizeof_priv, unsigned int txqs,
 }
 EXPORT_SYMBOL(alloc_etherdev_mqs);
 
-static void devm_free_netdev(struct device *dev, void *res)
-{
-	free_netdev(*(struct net_device **)res);
-}
-
-struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
-					   unsigned int txqs, unsigned int rxqs)
-{
-	struct net_device **dr;
-	struct net_device *netdev;
-
-	dr = devres_alloc(devm_free_netdev, sizeof(*dr), GFP_KERNEL);
-	if (!dr)
-		return NULL;
-
-	netdev = alloc_etherdev_mqs(sizeof_priv, txqs, rxqs);
-	if (!netdev) {
-		devres_free(dr);
-		return NULL;
-	}
-
-	*dr = netdev;
-	devres_add(dev, dr);
-
-	return netdev;
-}
-EXPORT_SYMBOL(devm_alloc_etherdev_mqs);
-
 ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len)
 {
 	return scnprintf(buf, PAGE_SIZE, "%*phC\n", len, addr);
-- 
2.25.0

[PATCH v2 3/5] net: devres: define a separate devres structure for devm_alloc_etherdev()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Not using a proxy structure to store struct net_device doesn't save
anything in terms of compiled code size or memory usage but significantly
decreases the readability of the code with all the pointer casting.

Define struct net_device_devres and use it in devm_alloc_etherdev_mqs().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 net/devres.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/devres.c b/net/devres.c
index c1465d9f9019..b97b0c5a8216 100644
--- a/net/devres.c
+++ b/net/devres.c
@@ -7,30 +7,34 @@
 #include <linux/etherdevice.h>
 #include <linux/netdevice.h>
 
-static void devm_free_netdev(struct device *dev, void *res)
+struct net_device_devres {
+	struct net_device *ndev;
+};
+
+static void devm_free_netdev(struct device *dev, void *this)
 {
-	free_netdev(*(struct net_device **)res);
+	struct net_device_devres *res = this;
+
+	free_netdev(res->ndev);
 }
 
 struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
 					   unsigned int txqs, unsigned int rxqs)
 {
-	struct net_device **dr;
-	struct net_device *netdev;
+	struct net_device_devres *dr;
 
 	dr = devres_alloc(devm_free_netdev, sizeof(*dr), GFP_KERNEL);
 	if (!dr)
 		return NULL;
 
-	netdev = alloc_etherdev_mqs(sizeof_priv, txqs, rxqs);
-	if (!netdev) {
+	dr->ndev = alloc_etherdev_mqs(sizeof_priv, txqs, rxqs);
+	if (!dr->ndev) {
 		devres_free(dr);
 		return NULL;
 	}
 
-	*dr = netdev;
 	devres_add(dev, dr);
 
-	return netdev;
+	return dr->ndev;
 }
 EXPORT_SYMBOL(devm_alloc_etherdev_mqs);
-- 
2.25.0

[PATCH v2 4/5] net: devres: provide devm_register_netdev()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Provide devm_register_netdev() - a device resource managed variant
of register_netdev(). This new helper will only work for net_device
structs that are also already managed by devres.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 .../driver-api/driver-model/devres.rst        |  1 +
 include/linux/netdevice.h                     |  2 +
 net/devres.c                                  | 55 +++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 50df28d20fa7..fc242ed4bde5 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -375,6 +375,7 @@ MUX
 NET
   devm_alloc_etherdev()
   devm_alloc_etherdev_mqs()
+  devm_register_netdev()
 
 PER-CPU MEM
   devm_alloc_percpu()
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a18f8fdf4260..1a96e9c4ec36 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4280,6 +4280,8 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 int register_netdev(struct net_device *dev);
 void unregister_netdev(struct net_device *dev);
 
+int devm_register_netdev(struct device *dev, struct net_device *ndev);
+
 /* General hardware address lists handling functions */
 int __hw_addr_sync(struct netdev_hw_addr_list *to_list,
 		   struct netdev_hw_addr_list *from_list, int addr_len);
diff --git a/net/devres.c b/net/devres.c
index b97b0c5a8216..57a6a88d11f6 100644
--- a/net/devres.c
+++ b/net/devres.c
@@ -38,3 +38,58 @@ struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
 	return dr->ndev;
 }
 EXPORT_SYMBOL(devm_alloc_etherdev_mqs);
+
+static void devm_netdev_release(struct device *dev, void *this)
+{
+	struct net_device_devres *res = this;
+
+	unregister_netdev(res->ndev);
+}
+
+static int netdev_devres_match(struct device *dev, void *this, void *match_data)
+{
+	struct net_device_devres *res = this;
+	struct net_device *ndev = match_data;
+
+	return ndev == res->ndev;
+}
+
+/**
+ *	devm_register_netdev - resource managed variant of register_netdev()
+ *	@dev: managing device for this netdev - usually the parent device
+ *	@ndev: device to register
+ *
+ *	This is a devres variant of register_netdev() for which the unregister
+ *	function will be call automatically when the managing device is
+ *	detached. Note: the net_device used must also be resource managed by
+ *	the same struct device.
+ */
+int devm_register_netdev(struct device *dev, struct net_device *ndev)
+{
+	struct net_device_devres *dr;
+	int ret;
+
+	/* struct net_device must itself be managed. For now a managed netdev
+	 * can only be allocated by devm_alloc_etherdev_mqs() so the check is
+	 * straightforward.
+	 */
+	if (WARN_ON(!devres_find(dev, devm_free_netdev,
+				 netdev_devres_match, ndev)))
+		return -EINVAL;
+
+	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);
-- 
2.25.0

[PATCH v2 5/5] net: ethernet: mtk_star_emac: use devm_register_netdev()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Use the new devres variant of register_netdev() in the mtk-star-emac
driver and shrink the code by a couple lines.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/net/ethernet/mediatek/mtk_star_emac.c | 17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_star_emac.c b/drivers/net/ethernet/mediatek/mtk_star_emac.c
index 789c77af501f..b74349cede28 100644
--- a/drivers/net/ethernet/mediatek/mtk_star_emac.c
+++ b/drivers/net/ethernet/mediatek/mtk_star_emac.c
@@ -1519,13 +1519,6 @@ static void mtk_star_mdiobus_unregister(void *data)
 	mdiobus_unregister(priv->mii);
 }
 
-static void mtk_star_unregister_netdev(void *data)
-{
-	struct net_device *ndev = data;
-
-	unregister_netdev(ndev);
-}
-
 static int mtk_star_probe(struct platform_device *pdev)
 {
 	struct device_node *of_node;
@@ -1641,15 +1634,7 @@ static int mtk_star_probe(struct platform_device *pdev)
 
 	netif_napi_add(ndev, &priv->napi, mtk_star_poll, MTK_STAR_NAPI_WEIGHT);
 
-	ret = register_netdev(ndev);
-	if (ret)
-		return ret;
-
-	ret = devm_add_action_or_reset(dev, mtk_star_unregister_netdev, ndev);
-	if (ret)
-		return ret;
-
-	return 0;
+	return devm_register_netdev(dev, ndev);
 }
 
 static const struct of_device_id mtk_star_of_match[] = {
-- 
2.25.0

Re: [PATCH v2 0/5] net: provide a devres variant of register_netdev()

[David Miller]

From: Bartosz Golaszewski <brgl@bgdev.pl>
Date: Sat, 23 May 2020 15:27:06 +0200

> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> Using devres helpers allows to shrink the probing code, avoid memory leaks in
> error paths make sure the order in which resources are freed is the exact
> opposite of their allocation. This series proposes to add a devres variant
> of register_netdev() that will only work with net_device structures whose
> memory is also managed.
> 
> First we add the missing documentation entry for the only other networking
> devres helper: devm_alloc_etherdev().
> 
> Next we move devm_alloc_etherdev() into a separate source file.
> 
> We then use a proxy structure in devm_alloc_etherdev() to improve readability.
> 
> Last: we implement devm_register_netdev() and use it in mtk-eth-mac driver.
> 
> v1 -> v2:
> - rebase on top of net-next after driver rename, no functional changes

Series applied, thank you.