regmap: mdio: Clean up invalid clause-22 addresses

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>
Link: https://lore.kernel.org/r/f7013f67e6d6ff56ec98660f18320f6ffcc1a777.1622743333.git.sander@svanheule.netSigned-off-by: Mark Brown <broonie@kernel.org>

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 = {