[PATCH net-next v4 05/13] devlink: support index-based lookup via bus_name/dev_name handle

[Jiri Pirko <jiri@resnulli.us>]

From: Jiri Pirko <jiri@nvidia.com>

Devlink instances without a backing device use bus_name
"devlink_index" and dev_name set to the decimal index string.
When user space sends this handle, detect the pattern and perform
a direct xarray lookup by index instead of iterating all instances.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
v2->v3:
- unify return value -ENODEV even in case non-numeric dev_name
v1->v2:
- moved DEVLINK_INDEX_BUS_NAME definition here from patch #7
---
 include/uapi/linux/devlink.h | 2 ++
 net/devlink/netlink.c        | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
index 1ba3436db4ae..7de2d8cc862f 100644
--- a/include/uapi/linux/devlink.h
+++ b/include/uapi/linux/devlink.h
@@ -19,6 +19,8 @@
 #define DEVLINK_GENL_VERSION 0x1
 #define DEVLINK_GENL_MCGRP_CONFIG_NAME "config"
 
+#define DEVLINK_INDEX_BUS_NAME "devlink_index"
+
 enum devlink_command {
 	/* don't change the order or add anything between, this is ABI! */
 	DEVLINK_CMD_UNSPEC,
diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 9cba40285de4..fa38fca22fe4 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -203,6 +203,15 @@ devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs,
 	busname = nla_data(attrs[DEVLINK_ATTR_BUS_NAME]);
 	devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
 
+	if (!strcmp(busname, DEVLINK_INDEX_BUS_NAME)) {
+		if (kstrtoul(devname, 10, &index))
+			return ERR_PTR(-ENODEV);
+		devlink = devlinks_xa_lookup_get(net, index);
+		if (!devlink)
+			return ERR_PTR(-ENODEV);
+		goto found;
+	}
+
 	devlinks_xa_for_each_registered_get(net, index, devlink) {
 		if (strcmp(devlink_bus_name(devlink), busname) == 0 &&
 		    strcmp(devlink_dev_name(devlink), devname) == 0)
-- 
2.51.1