Subject: [PATCH v2 5/5] net: dsa: exit probe if no switch were found

From: Neil Armstrong <[email-masked]>
Date: Sat, 3 Oct 2015 16:26:15 +0200

If no switch were found in dsa_setup_dst, return -ENODEV and
exit the dsa_probe cleanly.

Tested-by: Andrew Lunn <[email-masked]>
Tested-by: Florian Fainelli <[email-masked]>
Signed-off-by: Neil Armstrong <[email-masked]>
---
 net/dsa/dsa.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index dd171ff..9c521b7 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -836,10 +836,11 @@ static inline void dsa_of_remove(struct device *dev)
 }
 #endif

-static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
+static int dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
 			  struct device *parent, struct dsa_platform_data *pd)
 {
 	int i;
+	unsigned configured = 0;

 	dst->pd = pd;
 	dst->master_netdev = dev;
@@ -859,9 +860,17 @@ static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
 		dst->ds[i] = ds;
 		if (ds->drv->poll_link != NULL)
 			dst->link_poll_needed = 1;
+
+		++configured;
 	}

 	/*
+	 * If no switch was found, exit cleanly
+	 */
+	if (!configured)
+		return -EPROBE_DEFER;
+
+	/*
 	 * If we use a tagging format that doesn't have an ethertype
 	 * field, make sure that all packets from this point on get
 	 * sent to the tag format's receive function.
@@ -877,6 +886,8 @@ static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
 		dst->link_poll_timer.expires = round_jiffies(jiffies + HZ);
 		add_timer(&dst->link_poll_timer);
 	}
+
+	return 0;
 }

 static int dsa_probe(struct platform_device *pdev)
@@ -926,9 +937,9 @@ static int dsa_probe(struct platform_device *pdev)

 	platform_set_drvdata(pdev, dst);

-	dsa_setup_dst(dst, dev, &pdev->dev, pd);
-
-	return 0;
+	ret = dsa_setup_dst(dst, dev, &pdev->dev, pd);
+	if (!ret)
+		return 0;

 out:
 	dsa_of_remove(&pdev->dev);
-- 
1.9.1