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

[Vivien Didelot]

Hi Marek,

On Sun, 25 Aug 2019 05:59:12 +0200, Marek Behún <marek.be...@nic.cz> 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 <vivien.dide...@gmail.com>


Thank you!

        Vivien