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From:   Sander Vanheule <sander@svanheule.net>
To:     Mark Brown <broonie@kernel.org>, Andrew Lunn <andrew@lunn.ch>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Sander Vanheule <sander@svanheule.net>
Subject: [RFC PATCH 1/2] regmap: mdio: Clean up invalid clause-22 addresses
Date:   Thu,  3 Jun 2021 20:25:09 +0200
Message-Id: <f7013f67e6d6ff56ec98660f18320f6ffcc1a777.1622743333.git.sander@svanheule.net>
In-Reply-To: <cover.1622743333.git.sander@svanheule.net>
References: <cover.1622743333.git.sander@svanheule.net>
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Currently a regmap configuration for regmap-mdio must have a register
address width of 5 bits (cf. clause-22 register access). This is not
enforced on the provided register addresses, which would enable
clause-45 MDIO bus access, if the right bit packing is used.

Prevent clause-45 access, and other invalid addresses, by masking the
provided register address.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
---
 drivers/base/regmap/regmap-mdio.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/base/regmap/regmap-mdio.c b/drivers/base/regmap/regmap-mdio.c
index 5ec208279913..aee34bf2400e 100644
--- a/drivers/base/regmap/regmap-mdio.c
+++ b/drivers/base/regmap/regmap-mdio.c
@@ -5,16 +5,19 @@
 #include <linux/module.h>
 #include <linux/regmap.h>
 
+#define REGVAL_MASK		GENMASK(15, 0)
+#define REGNUM_C22_MASK		GENMASK(4, 0)
+
 static int regmap_mdio_read(void *context, unsigned int reg, unsigned int *val)
 {
 	struct mdio_device *mdio_dev = context;
 	int ret;
 
-	ret = mdiobus_read(mdio_dev->bus, mdio_dev->addr, reg);
+	ret = mdiobus_read(mdio_dev->bus, mdio_dev->addr, reg & REGNUM_C22_MASK);
 	if (ret < 0)
 		return ret;
 
-	*val = ret & 0xffff;
+	*val = ret & REGVAL_MASK;
 	return 0;
 }
 
@@ -22,7 +25,7 @@ static int regmap_mdio_write(void *context, unsigned int reg, unsigned int val)
 {
 	struct mdio_device *mdio_dev = context;
 
-	return mdiobus_write(mdio_dev->bus, mdio_dev->addr, reg, val);
+	return mdiobus_write(mdio_dev->bus, mdio_dev->addr, reg & REGNUM_C22_MASK, val);
 }
 
 static const struct regmap_bus regmap_mdio_bus = {
-- 
2.31.1