Re: [PATCH net-next v3 3/6] net: dsa: mv88e6xxx: create serdes_get_lane chip operation

Hi Marek,

On Sun, 25 Aug 2019 05:59:12 +0200, Marek Behún [off-list ref] wrote:

 void mv88e6390x_serdes_irq_free(struct mv88e6xxx_chip *chip, int port)
 {
-	int lane = mv88e6390x_serdes_get_lane(chip, port);
+	int err;
+	s8 lane;
 
-	if (lane == -ENODEV)
+	err = mv88e6xxx_serdes_get_lane(chip, port, &lane);
+	if (err) {
+		dev_err(chip->dev, "Unable to free SERDES irq: %d\n", err);
 		return;
-
+	}
 	if (lane < 0)
 		return;

[...]

-int mv88e6390x_serdes_get_lane(struct mv88e6xxx_chip *chip, int port);
+/* Put the SERDES lane address a port is using into *lane. If a port has
+ * multiple lanes, should put the first lane the port is using. If a port does
+ * not have a lane, put -1 into *lane.
+ */
+static inline int mv88e6xxx_serdes_get_lane(struct mv88e6xxx_chip *chip,
+					    int port, s8 *lane)
+{
+	if (!chip->info->ops->serdes_get_lane)
+		return -EOPNOTSUPP;
+
+	return chip->info->ops->serdes_get_lane(chip, port, lane);
+}

Using an invalid value is only useful if it can be interpreted by the other
functions of the API. So I would've make lane an u8, assuming it gets modified
only on success, which would result in calls like this one:

    u8 lane;
    int err;

    err = mv88e6xxx_serdes_get_lane(chip, port, &lane);
    if (err) {
        if (err == -ENODEV)
            err = 0;
        return err;
    }

But at least it is well documented, so we can eventually fine tuned later:

Reviewed-by: Vivien Didelot <redacted>


Thank you!

	Vivien