linux-kernel - [PATCH v2 net-next 3/3] net: mscc: ocelot: issue a warning if stats are incorrectly ordered

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Message-Id: <20221119231406.3167852-4-colin.foster@in-advantage.com>
Date:   Sat, 19 Nov 2022 15:14:06 -0800
From:   Colin Foster <colin.foster@...advantage.com>
To:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc:     Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>, UNGLinuxDriver@...rochip.com,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: [PATCH v2 net-next 3/3] net: mscc: ocelot: issue a warning if stats are incorrectly ordered

Ocelot uses regmap_bulk_read() operations to efficiently read stats
registers. Currently the implementation relies on the stats layout to be
ordered to be most efficient.

Issue a warning if any future implementations happen to break this pattern.

Signed-off-by: Colin Foster <colin.foster@...advantage.com>
Co-developed-by: Vladimir Oltean <vladimir.oltean@....com>
---

v1->v2
    * New patch, picked up from previous mailings

---
 drivers/net/ethernet/mscc/ocelot_stats.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mscc/ocelot_stats.c b/drivers/net/ethernet/mscc/ocelot_stats.c
index 68e9f450c468..1478c3b21af1 100644
--- a/drivers/net/ethernet/mscc/ocelot_stats.c
+++ b/drivers/net/ethernet/mscc/ocelot_stats.c
@@ -602,7 +602,7 @@ EXPORT_SYMBOL(ocelot_port_get_stats64);
 static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
 {
 	struct ocelot_stats_region *region = NULL;
-	unsigned int last;
+	unsigned int last = 0;
 	int i;
 
 	INIT_LIST_HEAD(&ocelot->stats_regions);
@@ -619,6 +619,12 @@ static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
 			if (!region)
 				return -ENOMEM;
 
+			/* enum ocelot_stat must be kept sorted in the same
+			 * order as ocelot_stats_layout[i].reg in order to have
+			 * efficient bulking
+			 */
+			WARN_ON(last >= ocelot_stats_layout[i].reg);
+
 			region->base = ocelot_stats_layout[i].reg;
 			region->count = 1;
 			list_add_tail(&region->node, &ocelot->stats_regions);
-- 
2.25.1