devlink: allow devlink instance allocation without a backing device

Allow devlink_alloc_ns() to be called with dev=NULL to support
device-less devlink instances. When dev is NULL, the instance is
identified over netlink using "devlink_index" as bus_name and
the decimal index value as dev_name.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20260312100407.551173-11-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 25 insertions, 11 deletions

diff --git a/net/devlink/core.c b/net/devlink/core.c
index 34eb06d88544..eeb6a71f5f56 100644
--- a/net/devlink/core.c
+++ b/net/devlink/core.c
@@ -250,13 +250,13 @@ EXPORT_SYMBOL_GPL(devlink_to_dev);
 
 const char *devlink_bus_name(const struct devlink *devlink)
 {
-	return devlink->dev->bus->name;
+	return devlink->dev ? devlink->dev->bus->name : DEVLINK_INDEX_BUS_NAME;
 }
 EXPORT_SYMBOL_GPL(devlink_bus_name);
 
 const char *devlink_dev_name(const struct devlink *devlink)
 {
-	return dev_name(devlink->dev);
+	return devlink->dev ? dev_name(devlink->dev) : devlink->dev_name_index;
 }
 EXPORT_SYMBOL_GPL(devlink_dev_name);
 
@@ -329,7 +329,10 @@ static void devlink_release(struct work_struct *work)
 
 	mutex_destroy(&devlink->lock);
 	lockdep_unregister_key(&devlink->lock_key);
-	put_device(devlink->dev);
+	if (devlink->dev)
+		put_device(devlink->dev);
+	else
+		kfree(devlink->dev_name_index);
 	kvfree(devlink);
 }
 
@@ -432,7 +435,7 @@ struct devlink *__devlink_alloc(const struct devlink_ops *ops, size_t priv_size,
 	static u32 last_id;
 	int ret;
 
-	WARN_ON(!ops || !dev || !dev_driver);
+	WARN_ON(!ops || !dev_driver);
 	if (!devlink_reload_actions_valid(ops))
 		return NULL;
 
@@ -445,7 +448,14 @@ struct devlink *__devlink_alloc(const struct devlink_ops *ops, size_t priv_size,
 	if (ret < 0)
 		goto err_xa_alloc;
 
-	devlink->dev = get_device(dev);
+	if (dev) {
+		devlink->dev = get_device(dev);
+	} else {
+		devlink->dev_name_index = kasprintf(GFP_KERNEL, "%u", devlink->index);
+		if (!devlink->dev_name_index)
+			goto err_kasprintf;
+	}
+
 	devlink->ops = ops;
 	devlink->dev_driver = dev_driver;
 	xa_init_flags(&devlink->ports, XA_FLAGS_ALLOC);
@@ -471,6 +481,8 @@ struct devlink *__devlink_alloc(const struct devlink_ops *ops, size_t priv_size,
 
 	return devlink;
 
+err_kasprintf:
+	xa_erase(&devlinks, devlink->index);
 err_xa_alloc:
 	kvfree(devlink);
 	return NULL;
@@ -492,6 +504,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
 				 size_t priv_size, struct net *net,
 				 struct device *dev)
 {
+	WARN_ON(!dev);
 	return __devlink_alloc(ops, priv_size, net, dev, dev->driver);
 }
 EXPORT_SYMBOL_GPL(devlink_alloc_ns);
diff --git a/net/devlink/dev.c b/net/devlink/dev.c
index e3a36de4f4ae..57b2b8f03543 100644
--- a/net/devlink/dev.c
+++ b/net/devlink/dev.c
@@ -453,7 +453,8 @@ int devlink_reload(struct devlink *devlink, struct net *dest_net,
 	 * (e.g., PCI reset) and to close possible races between these
 	 * operations and probe/remove.
 	 */
-	device_lock_assert(devlink->dev);
+	if (devlink->dev)
+		device_lock_assert(devlink->dev);
 
 	memcpy(remote_reload_stats, devlink->stats.remote_reload_stats,
 	       sizeof(remote_reload_stats));
@@ -854,7 +855,7 @@ int devlink_info_version_running_put_ext(struct devlink_info_req *req,
 }
 EXPORT_SYMBOL_GPL(devlink_info_version_running_put_ext);
 
-static int devlink_nl_driver_info_get(struct device_driver *drv,
+static int devlink_nl_driver_info_get(const struct device_driver *drv,
 				      struct devlink_info_req *req)
 {
 	if (!drv)
@@ -872,7 +873,6 @@ devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
 		     enum devlink_command cmd, u32 portid,
 		     u32 seq, int flags, struct netlink_ext_ack *extack)
 {
-	struct device *dev = devlink_to_dev(devlink);
 	struct devlink_info_req req = {};
 	void *hdr;
 	int err;
@@ -892,7 +892,7 @@ devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
 			goto err_cancel_msg;
 	}
 
-	err = devlink_nl_driver_info_get(dev->driver, &req);
+	err = devlink_nl_driver_info_get(devlink->dev_driver, &req);
 	if (err)
 		goto err_cancel_msg;
 
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index cb2ffef1ac2d..7dfb7cdd2d23 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h
@@ -49,6 +49,7 @@ struct devlink {
 	struct xarray snapshot_ids;
 	struct devlink_dev_stats stats;
 	struct device *dev;
+	const char *dev_name_index;
 	const struct device_driver *dev_driver;
 	possible_net_t _net;
 	/* Serializes access to devlink instance specific objects such as
@@ -119,7 +120,7 @@ static inline bool devl_is_registered(struct devlink *devlink)
 
 static inline void devl_dev_lock(struct devlink *devlink, bool dev_lock)
 {
-	if (dev_lock)
+	if (dev_lock && devlink->dev)
 		device_lock(devlink->dev);
 	devl_lock(devlink);
 }
@@ -127,7 +128,7 @@ static inline void devl_dev_lock(struct devlink *devlink, bool dev_lock)
 static inline void devl_dev_unlock(struct devlink *devlink, bool dev_lock)
 {
 	devl_unlock(devlink);
-	if (dev_lock)
+	if (dev_lock && devlink->dev)
 		device_unlock(devlink->dev);
 }