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

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

[Markus Elfring]

…
> +++ b/net/devres.c
> @@ -38,3 +38,58 @@ struct net_device *devm_alloc_etherdev_mqs(struct device *dev, int sizeof_priv,
…
> + *	This is a devres variant of register_netdev() for which the unregister
> + *	function will be call automatically when the managing device is

Is the following wording variant more appropriate?

+ *	function will be automatically called when the managing device is


Regards,
Markus

[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 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