netdev - [PATCH net-next 12/15] dsa: Make use of the list of tag drivers

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Date:   Thu, 18 Apr 2019 04:31:17 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: [PATCH net-next 12/15] dsa: Make use of the list of tag drivers

Implement the _get and _put functions to make use of the list of tag
drivers. Also, trigger the loading of the module, based on the alias
information. The _get function takes a reference on the tag driver, so
it cannot be unloaded, and the _put function releases the reference.

Signed-off-by: Andrew Lunn <andrew@...n.ch>
---
 net/dsa/dsa.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index a3210b2f88a2..17d26cc7a128 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -129,20 +129,38 @@ const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops)
 
 const struct dsa_device_ops *dsa_tag_driver_get(int tag_protocol)
 {
-	const struct dsa_device_ops *ops;
+	struct dsa_device_ops *ops;
+	char module_name[128];
+	bool found = false;
 
-	if (tag_protocol >= DSA_TAG_LAST)
-		return ERR_PTR(-EINVAL);
-	ops = dsa_device_ops[tag_protocol];
+	snprintf(module_name, 127, "%s%d", DSA_TAG_DRIVER_ALIAS,
+		 tag_protocol);
 
-	if (!ops)
-		return ERR_PTR(-ENOPROTOOPT);
+	request_module(module_name);
+
+	mutex_lock(&dsa_tag_drivers_lock);
+	list_for_each_entry(ops, &dsa_tag_drivers_list, list) {
+		if (ops->proto == tag_protocol) {
+			found = true;
+			break;
+		}
+	}
+
+	if (found) {
+		if (!try_module_get(ops->owner))
+			ops = ERR_PTR(-ENOPROTOOPT);
+	} else {
+		ops = ERR_PTR(-ENOPROTOOPT);
+	}
+
+	mutex_unlock(&dsa_tag_drivers_lock);
 
 	return ops;
 }
 
 void dsa_tag_driver_put(const struct dsa_device_ops *ops)
 {
+	module_put(ops->owner);
 }
 
 static int dev_is_class(struct device *dev, void *class)
-- 
2.20.1