netdev - Re: [PATCH net-next v3 3/6] net: dsa: mv88e6xxx: create serdes_get

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Message-ID: <20190825114825.GD6729@t480s.localdomain>
Date:   Sun, 25 Aug 2019 11:48:25 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Marek Behún <marek.behun@....cz>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Marek Behún <marek.behun@....cz>
Subject: 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 <marek.behun@....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.didelot@...il.com>


Thank you!

	Vivien