netdev - Re: [PATCH net-next 06/17] net: dsa: Call driver's setup callback after setting up its switchdev notifier

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Date:   Tue, 2 Apr 2019 23:03:49 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     f.fainelli@...il.com, vivien.didelot@...il.com,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
        georg.waibel@...sor-technik.de
Subject: Re: [PATCH net-next 06/17] net: dsa: Call driver's setup callback
 after setting up its switchdev notifier

On Sun, Mar 31, 2019 at 08:42:21PM +0300, Vladimir Oltean wrote:
> This allows the driver to perform some manipulations of its own during
> setup, using generic code.
> One current usage scenario is for the driver to request DSA to set up
> 802.1Q based switch tagging for its ports.
> 
> Signed-off-by: Vladimir Oltean <olteanv@...il.com>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  net/dsa/dsa2.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
> index c00ee464afc7..5beceb18b7e2 100644
> --- a/net/dsa/dsa2.c
> +++ b/net/dsa/dsa2.c
> @@ -360,14 +360,14 @@ static int dsa_switch_setup(struct dsa_switch *ds)
>  	if (err)
>  		return err;
>  
> -	err = ds->ops->setup(ds);
> -	if (err < 0)
> -		return err;
> -
>  	err = dsa_switch_register_notifier(ds);
>  	if (err)
>  		return err;

It seems that notifiers are the important thing here? Maybe state that
in the commit message?

I'm also wondering how safe this is in general. If we have not yet
called the driver setup, the switch is potentially not yet ready to
actually handle an requests that come via the notifier. If such
notifiers can only come from the driver itself, it should be
safe. However, if they could come from the rest of the stack, i could
see bad things happening.

    Andrew