From: Jiri Pirko <[email protected]>

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 <[email protected]>
---
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 b73cec31089f..127f337489c0 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -200,6 +200,15 @@ 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(-EINVAL);
+               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, busname) == 0 &&
                    strcmp(devlink->dev_name, devname) == 0)
-- 
2.51.1


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