Subject: Re: [RFC PATCH 3/3] net: dsa: exit probe if no switch were found

From: Neil Armstrong <[email-masked]>
Date: Thu, 1 Oct 2015 17:27:32 +0200

On 09/30/2015 10:21 AM, Neil Armstrong wrote:
> If no switch were found in dsa_setup_dst, return -ENODEV and
> exit the dsa_probe cleanly.
> 
> Signed-off-by: Neil Armstrong <[email-masked]>
> ---
>  net/dsa/dsa.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index 0c104af..6ae1ab9 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -844,10 +844,11 @@ static inline void dsa_of_remove(struct device *dev)
>  }
>  #endif
> 
> -static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
> +static int dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
>  			  struct device *parent, struct dsa_platform_data *pd)
>  {
>  	int i;
> +	unsigned configured = 0;
> 
>  	dst->pd = pd;
>  	dst->master_netdev = dev;
> @@ -867,9 +868,17 @@ static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
>  		dst->ds[i] = ds;
>  		if (ds->drv->poll_link != NULL)
>  			dst->link_poll_needed = 1;
> +
> +		++configured;
>  	}
> 
>  	/*
> +	 * If no switch was found, exit cleanly
> +	 */
> +	if (!configured)
> +		return -ENODEV;
> +
> +	/*
>  	 * If we use a tagging format that doesn't have an ethertype
>  	 * field, make sure that all packets from this point on get
>  	 * sent to the tag format's receive function.
> @@ -885,6 +894,8 @@ static void dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
>  		dst->link_poll_timer.expires = round_jiffies(jiffies + HZ);
>  		add_timer(&dst->link_poll_timer);
>  	}
> +
> +	return 0;
>  }
> 
>  static int dsa_probe(struct platform_device *pdev)
> @@ -934,9 +945,9 @@ static int dsa_probe(struct platform_device *pdev)
> 
>  	platform_set_drvdata(pdev, dst);
> 
> -	dsa_setup_dst(dst, dev, &pdev->dev, pd);
> -
> -	return 0;
> +	ret = dsa_setup_dst(dst, dev, &pdev->dev, pd);
> +	if (!ret)
> +		return 0;
> 
>  out:
>  	dsa_of_remove(&pdev->dev);
> 

Couldn't we use the probe defer mechanism here ? (until complete rework is done)

How could we re-probe after a register_switch_driver ?

Neil