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net: dsa: fix error code getting shifted with 4 in dsa_slave_get_sset_count

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[ Upstream commit b94cbc909f1d80378a1f541968309e5c1178c98b ]

DSA implements a bunch of 'standardized' ethtool statistics counters,
namely tx_packets, tx_bytes, rx_packets, rx_bytes. So whatever the
hardware driver returns in .get_sset_count(), we need to add 4 to that.

That is ok, except that .get_sset_count() can return a negative error
code, for example:

b53_get_sset_count
-> phy_ethtool_get_sset_count
   -> return -EIO

-EIO is -5, and with 4 added to it, it becomes -1, aka -EPERM. One can
imagine that certain error codes may even become positive, although
based on code inspection I did not see instances of that.

Check the error code first, if it is negative return it as-is.

Based on a similar patch for dsa_master_get_strings from Dan Carpenter:
https://patchwork.kernel.org/project/netdevbpf/patch/YJaSe3RPgn7gKxZv@mwanda/

Fixes: 91da11f870 ("net: Distributed Switch Architecture protocol support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Vladimir Oltean 2021-05-09 22:33:38 +03:00 committed by Greg Kroah-Hartman
parent 4450f733dc
commit 87803141fb
1 changed files with 7 additions and 5 deletions
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12
net/dsa/slave.c
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@ -692,13 +692,15 @@ static int dsa_slave_get_sset_count(struct net_device *dev, int sset)
struct dsa_switch *ds = dp->ds;
if (sset == ETH_SS_STATS) {
int count;
int count = 0;
count = 4;
if (ds->ops->get_sset_count)
count += ds->ops->get_sset_count(ds, dp->index, sset);
if (ds->ops->get_sset_count) {
count = ds->ops->get_sset_count(ds, dp->index, sset);
if (count < 0)
return count;
}
return count;
return count + 4;
}
return -EOPNOTSUPP;