Merge branch 'wwan-link-creation'

Loic Poulain says:

====================
net: Add WWAN link creation support

Most of the modern WWAN modems are able to support multiple network
contexts, allowing user to connect to different APNs (e.g. Internet,
MMS, etc...). These contexts are usually dynamically configured via
a control channel such as MBIM, QMI or AT.

Each context is naturally represented as a network link/device, and
the muxing of these links is usually vendor/bus specific (QMAP, MBIM,
intel iosm...). Today some drivers create a static collection of
netdevs at init time, some relies on VLAN link for associating a context
(cdc-mbim), some exposes sysfs attribute for dynamically creating
additional netdev (qmi_wwan add_mux attr) or relies on vendor specific
link type (rmnet) for performing the muxing... so there is no generic
way to handle WWAN links, making user side integration painful.

This series introduces a generic WWAN link management interface to the
WWAN framework, allowing user to dynamically create and remove WWAN
links through rtnetlink ('wwan' type). The underlying 'muxing' vendor
implementation is completely abstracted.

The idea is to use this interface for upcoming WWAN drivers (intel
iosm) and to progressively integrate support into existing ones
(qmi_wwan, cdc-mbim, mhi_net, etc...).

v2: - Squashed Johannes and Sergey changes
    - Added IFLA_PARENT_DEV_BUS_NAME attribute
    - reworded commit message + introduce Sergey's comment

v3: - Added basic new interface user to this series (mhi_net)
    - Moved IFLA_PARENT_DEV_NAME nla_policy introduction to right patch
    - Added cover letter
    - moved kdoc to .c file
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 339 insertions, 30 deletions

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 4da68ba8448f..30d6e2f7686e 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -431,6 +431,7 @@ config VSOCKMON
 config MHI_NET
 	tristate "MHI network driver"
 	depends on MHI_BUS
+	select WWAN_CORE
 	help
 	  This is the network driver for MHI bus.  It can be used with
 	  QCOM based WWAN modems (like SDX55).  Say Y or M.
diff --git a/drivers/net/mhi/net.c b/drivers/net/mhi/net.c
index 0d8293a47a56..64af1e518484 100644
--- a/drivers/net/mhi/net.c
+++ b/drivers/net/mhi/net.c
@@ -11,6 +11,7 @@
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
 #include <linux/u64_stats_sync.h>
+#include <linux/wwan.h>
 
 #include "mhi.h"
 
@@ -18,6 +19,12 @@
 #define MHI_NET_MAX_MTU		0xffff
 #define MHI_NET_DEFAULT_MTU	0x4000
 
+/* When set to false, the default netdev (link 0) is not created, and it's up
+ * to user to create the link (via wwan rtnetlink).
+ */
+static bool create_default_iface = true;
+module_param(create_default_iface, bool, 0);
+
 struct mhi_device_info {
 	const char *netname;
 	const struct mhi_net_proto *proto;
@@ -295,32 +302,33 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
 		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
 }
 
-static struct device_type wwan_type = {
-	.name = "wwan",
-};
-
-static int mhi_net_probe(struct mhi_device *mhi_dev,
-			 const struct mhi_device_id *id)
+static int mhi_net_newlink(void *ctxt, struct net_device *ndev, u32 if_id,
+			   struct netlink_ext_ack *extack)
 {
-	const struct mhi_device_info *info = (struct mhi_device_info *)id->driver_data;
-	struct device *dev = &mhi_dev->dev;
+	const struct mhi_device_info *info;
+	struct mhi_device *mhi_dev = ctxt;
 	struct mhi_net_dev *mhi_netdev;
-	struct net_device *ndev;
 	int err;
 
-	ndev = alloc_netdev(sizeof(*mhi_netdev), info->netname,
-			    NET_NAME_PREDICTABLE, mhi_net_setup);
-	if (!ndev)
-		return -ENOMEM;
+	info = (struct mhi_device_info *)mhi_dev->id->driver_data;
+
+	/* For now we only support one link (link context 0), driver must be
+	 * reworked to break 1:1 relationship for net MBIM and to forward setup
+	 * call to rmnet(QMAP) otherwise.
+	 */
+	if (if_id != 0)
+		return -EINVAL;
+
+	if (dev_get_drvdata(&mhi_dev->dev))
+		return -EBUSY;
 
 	mhi_netdev = netdev_priv(ndev);
-	dev_set_drvdata(dev, mhi_netdev);
+
+	dev_set_drvdata(&mhi_dev->dev, mhi_netdev);
 	mhi_netdev->ndev = ndev;
 	mhi_netdev->mdev = mhi_dev;
 	mhi_netdev->skbagg_head = NULL;
 	mhi_netdev->proto = info->proto;
-	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
-	SET_NETDEV_DEVTYPE(ndev, &wwan_type);
 
 	INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
 	u64_stats_init(&mhi_netdev->stats.rx_syncp);
@@ -334,7 +342,10 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
 	/* Number of transfer descriptors determines size of the queue */
 	mhi_netdev->rx_queue_sz = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
 
-	err = register_netdev(ndev);
+	if (extack)
+		err = register_netdevice(ndev);
+	else
+		err = register_netdev(ndev);
 	if (err)
 		goto out_err;
 
@@ -347,23 +358,89 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
 	return 0;
 
 out_err_proto:
-	unregister_netdev(ndev);
+	unregister_netdevice(ndev);
 out_err:
 	free_netdev(ndev);
 	return err;
 }
 
-static void mhi_net_remove(struct mhi_device *mhi_dev)
+static void mhi_net_dellink(void *ctxt, struct net_device *ndev,
+			    struct list_head *head)
 {
-	struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
+	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);
+	struct mhi_device *mhi_dev = ctxt;
 
-	unregister_netdev(mhi_netdev->ndev);
+	if (head)
+		unregister_netdevice_queue(ndev, head);
+	else
+		unregister_netdev(ndev);
 
-	mhi_unprepare_from_transfer(mhi_netdev->mdev);
+	mhi_unprepare_from_transfer(mhi_dev);
 
 	kfree_skb(mhi_netdev->skbagg_head);
 
-	free_netdev(mhi_netdev->ndev);
+	dev_set_drvdata(&mhi_dev->dev, NULL);
+}
+
+const struct wwan_ops mhi_wwan_ops = {
+	.owner = THIS_MODULE,
+	.priv_size = sizeof(struct mhi_net_dev),
+	.setup = mhi_net_setup,
+	.newlink = mhi_net_newlink,
+	.dellink = mhi_net_dellink,
+};
+
+static int mhi_net_probe(struct mhi_device *mhi_dev,
+			 const struct mhi_device_id *id)
+{
+	const struct mhi_device_info *info = (struct mhi_device_info *)id->driver_data;
+	struct mhi_controller *cntrl = mhi_dev->mhi_cntrl;
+	struct net_device *ndev;
+	int err;
+
+	err = wwan_register_ops(&cntrl->mhi_dev->dev, &mhi_wwan_ops, mhi_dev);
+	if (err)
+		return err;
+
+	if (!create_default_iface)
+		return 0;
+
+	/* Create a default interface which is used as either RMNET real-dev,
+	 * MBIM link 0 or ip link 0)
+	 */
+	ndev = alloc_netdev(sizeof(struct mhi_net_dev), info->netname,
+			    NET_NAME_PREDICTABLE, mhi_net_setup);
+	if (!ndev) {
+		err = -ENOMEM;
+		goto err_unregister;
+	}
+
+	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
+
+	err = mhi_net_newlink(mhi_dev, ndev, 0, NULL);
+	if (err)
+		goto err_release;
+
+	return 0;
+
+err_release:
+	free_netdev(ndev);
+err_unregister:
+	wwan_unregister_ops(&cntrl->mhi_dev->dev);
+
+	return err;
+}
+
+static void mhi_net_remove(struct mhi_device *mhi_dev)
+{
+	struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
+	struct mhi_controller *cntrl = mhi_dev->mhi_cntrl;
+
+	/* rtnetlink takes care of removing remaining links */
+	wwan_unregister_ops(&cntrl->mhi_dev->dev);
+
+	if (create_default_iface)
+		mhi_net_dellink(mhi_dev, mhi_netdev->ndev, NULL);
 }
 
 static const struct mhi_device_info mhi_hwip0 = {
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 45a41aee8958..7e728042fc41 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -14,6 +14,8 @@
 #include <linux/types.h>
 #include <linux/termios.h>
 #include <linux/wwan.h>
+#include <net/rtnetlink.h>
+#include <uapi/linux/wwan.h>
 
 /* Maximum number of minors in use */
 #define WWAN_MAX_MINORS		(1 << MINORBITS)
@@ -35,10 +37,16 @@ static int wwan_major;
  *
  * @id: WWAN device unique ID.
  * @dev: Underlying device.
+ * @port_id: Current available port ID to pick.
+ * @ops: wwan device ops
+ * @ops_ctxt: context to pass to ops
  */
 struct wwan_device {
 	unsigned int id;
 	struct device dev;
+	atomic_t port_id;
+	const struct wwan_ops *ops;
+	void *ops_ctxt;
 };
 
 /**
@@ -102,7 +110,8 @@ static const struct device_type wwan_dev_type = {
 
 static int wwan_dev_parent_match(struct device *dev, const void *parent)
 {
-	return (dev->type == &wwan_dev_type && dev->parent == parent);
+	return (dev->type == &wwan_dev_type &&
+		(dev->parent == parent || dev == parent));
 }
 
 static struct wwan_device *wwan_dev_get_by_parent(struct device *parent)
@@ -116,6 +125,23 @@ static struct wwan_device *wwan_dev_get_by_parent(struct device *parent)
 	return to_wwan_dev(dev);
 }
 
+static int wwan_dev_name_match(struct device *dev, const void *name)
+{
+	return dev->type == &wwan_dev_type &&
+	       strcmp(dev_name(dev), name) == 0;
+}
+
+static struct wwan_device *wwan_dev_get_by_name(const char *name)
+{
+	struct device *dev;
+
+	dev = class_find_device(wwan_class, NULL, name, wwan_dev_name_match);
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
+	return to_wwan_dev(dev);
+}
+
 /* This function allocates and registers a new WWAN device OR if a WWAN device
  * already exist for the given parent, it gets a reference and return it.
  * This function is not exported (for now), it is called indirectly via
@@ -180,9 +206,14 @@ static void wwan_remove_dev(struct wwan_device *wwandev)
 	/* WWAN device is created and registered (get+add) along with its first
 	 * child port, and subsequent port registrations only grab a reference
 	 * (get). The WWAN device must then be unregistered (del+put) along with
-	 * its latest port, and reference simply dropped (put) otherwise.
+	 * its last port, and reference simply dropped (put) otherwise. In the
+	 * same fashion, we must not unregister it when the ops are still there.
 	 */
-	ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child);
+	if (wwandev->ops)
+		ret = 1;
+	else
+		ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child);
+
 	if (!ret)
 		device_unregister(&wwandev->dev);
 	else
@@ -750,26 +781,226 @@ static const struct file_operations wwan_port_fops = {
 	.llseek = noop_llseek,
 };
 
+/**
+ * wwan_register_ops - register WWAN device ops
+ * @parent: Device to use as parent and shared by all WWAN ports and
+ *	created netdevs
+ * @ops: operations to register
+ * @ctxt: context to pass to operations
+ *
+ * Returns: 0 on success, a negative error code on failure
+ */
+int wwan_register_ops(struct device *parent, const struct wwan_ops *ops,
+		      void *ctxt)
+{
+	struct wwan_device *wwandev;
+
+	if (WARN_ON(!parent || !ops))
+		return -EINVAL;
+
+	wwandev = wwan_create_dev(parent);
+	if (!wwandev)
+		return -ENOMEM;
+
+	if (WARN_ON(wwandev->ops)) {
+		wwan_remove_dev(wwandev);
+		return -EBUSY;
+	}
+
+	if (!try_module_get(ops->owner)) {
+		wwan_remove_dev(wwandev);
+		return -ENODEV;
+	}
+
+	wwandev->ops = ops;
+	wwandev->ops_ctxt = ctxt;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(wwan_register_ops);
+
+/**
+ * wwan_unregister_ops - remove WWAN device ops
+ * @parent: Device to use as parent and shared by all WWAN ports and
+ *	created netdevs
+ */
+void wwan_unregister_ops(struct device *parent)
+{
+	struct wwan_device *wwandev = wwan_dev_get_by_parent(parent);
+	bool has_ops;
+
+	if (WARN_ON(IS_ERR(wwandev)))
+		return;
+
+	has_ops = wwandev->ops;
+
+	/* put the reference obtained by wwan_dev_get_by_parent(),
+	 * we should still have one (that the owner is giving back
+	 * now) due to the ops being assigned, check that below
+	 * and return if not.
+	 */
+	put_device(&wwandev->dev);
+
+	if (WARN_ON(!has_ops))
+		return;
+
+	module_put(wwandev->ops->owner);
+
+	wwandev->ops = NULL;
+	wwandev->ops_ctxt = NULL;
+	wwan_remove_dev(wwandev);
+}
+EXPORT_SYMBOL_GPL(wwan_unregister_ops);
+
+static int wwan_rtnl_validate(struct nlattr *tb[], struct nlattr *data[],
+			      struct netlink_ext_ack *extack)
+{
+	if (!data)
+		return -EINVAL;
+
+	if (!tb[IFLA_PARENT_DEV_NAME])
+		return -EINVAL;
+
+	if (!data[IFLA_WWAN_LINK_ID])
+		return -EINVAL;
+
+	return 0;
+}
+
+static struct device_type wwan_type = { .name = "wwan" };
+
+static struct net_device *wwan_rtnl_alloc(struct nlattr *tb[],
+					  const char *ifname,
+					  unsigned char name_assign_type,
+					  unsigned int num_tx_queues,
+					  unsigned int num_rx_queues)
+{
+	const char *devname = nla_data(tb[IFLA_PARENT_DEV_NAME]);
+	struct wwan_device *wwandev = wwan_dev_get_by_name(devname);
+	struct net_device *dev;
+
+	if (IS_ERR(wwandev))
+		return ERR_CAST(wwandev);
+
+	/* only supported if ops were registered (not just ports) */
+	if (!wwandev->ops) {
+		dev = ERR_PTR(-EOPNOTSUPP);
+		goto out;
+	}
+
+	dev = alloc_netdev_mqs(wwandev->ops->priv_size, ifname, name_assign_type,
+			       wwandev->ops->setup, num_tx_queues, num_rx_queues);
+
+	if (dev) {
+		SET_NETDEV_DEV(dev, &wwandev->dev);
+		SET_NETDEV_DEVTYPE(dev, &wwan_type);
+	}
+
+out:
+	/* release the reference */
+	put_device(&wwandev->dev);
+	return dev;
+}
+
+static int wwan_rtnl_newlink(struct net *src_net, struct net_device *dev,
+			     struct nlattr *tb[], struct nlattr *data[],
+			     struct netlink_ext_ack *extack)
+{
+	struct wwan_device *wwandev = wwan_dev_get_by_parent(dev->dev.parent);
+	u32 link_id = nla_get_u32(data[IFLA_WWAN_LINK_ID]);
+	int ret;
+
+	if (IS_ERR(wwandev))
+		return PTR_ERR(wwandev);
+
+	/* shouldn't have a netdev (left) with us as parent so WARN */
+	if (WARN_ON(!wwandev->ops)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	if (wwandev->ops->newlink)
+		ret = wwandev->ops->newlink(wwandev->ops_ctxt, dev,
+					    link_id, extack);
+	else
+		ret = register_netdevice(dev);
+
+out:
+	/* release the reference */
+	put_device(&wwandev->dev);
+	return ret;
+}
+
+static void wwan_rtnl_dellink(struct net_device *dev, struct list_head *head)
+{
+	struct wwan_device *wwandev = wwan_dev_get_by_parent(dev->dev.parent);
+
+	if (IS_ERR(wwandev))
+		return;
+
+	/* shouldn't have a netdev (left) with us as parent so WARN */
+	if (WARN_ON(!wwandev->ops))
+		goto out;
+
+	if (wwandev->ops->dellink)
+		wwandev->ops->dellink(wwandev->ops_ctxt, dev, head);
+	else
+		unregister_netdevice(dev);
+
+out:
+	/* release the reference */
+	put_device(&wwandev->dev);
+}
+
+static const struct nla_policy wwan_rtnl_policy[IFLA_WWAN_MAX + 1] = {
+	[IFLA_WWAN_LINK_ID] = { .type = NLA_U32 },
+};
+
+static struct rtnl_link_ops wwan_rtnl_link_ops __read_mostly = {
+	.kind = "wwan",
+	.maxtype = __IFLA_WWAN_MAX,
+	.alloc = wwan_rtnl_alloc,
+	.validate = wwan_rtnl_validate,
+	.newlink = wwan_rtnl_newlink,
+	.dellink = wwan_rtnl_dellink,
+	.policy = wwan_rtnl_policy,
+};
+
 static int __init wwan_init(void)
 {
+	int err;
+
+	err = rtnl_link_register(&wwan_rtnl_link_ops);
+	if (err)
+		return err;
+
 	wwan_class = class_create(THIS_MODULE, "wwan");
-	if (IS_ERR(wwan_class))
-		return PTR_ERR(wwan_class);
+	if (IS_ERR(wwan_class)) {
+		err = PTR_ERR(wwan_class);
+		goto unregister;
+	}
 
 	/* chrdev used for wwan ports */
 	wwan_major = __register_chrdev(0, 0, WWAN_MAX_MINORS, "wwan_port",
 				       &wwan_port_fops);
 	if (wwan_major < 0) {
-		class_destroy(wwan_class);
-		return wwan_major;
+		err = wwan_major;
+		goto destroy;
 	}
 
 	return 0;
+
+destroy:
+	class_destroy(wwan_class);
+unregister:
+	rtnl_link_unregister(&wwan_rtnl_link_ops);
+	return err;
 }
 
 static void __exit wwan_exit(void)
 {
 	__unregister_chrdev(wwan_major, 0, WWAN_MAX_MINORS, "wwan_port");
+	rtnl_link_unregister(&wwan_rtnl_link_ops);
 	class_destroy(wwan_class);
 }