netdev - Re: [RFC PATCH net-next 1/6] net: dsa: make dp->bridge

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Date:   Thu, 11 Nov 2021 12:45:28 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Alvin Šipraga <ALSI@...g-olufsen.dk>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Tobias Waldekranz <tobias@...dekranz.com>,
        DENG Qingfang <dqfext@...il.com>
Subject: Re: [RFC PATCH net-next 1/6] net: dsa: make dp->bridge_num one-based

On Thu, Nov 11, 2021 at 12:24:47PM +0000, Alvin Šipraga wrote:
> On 10/26/21 18:26, Vladimir Oltean wrote:
> > I have seen too many bugs already due to the fact that we must encode an
> > invalid dp->bridge_num as a negative value, because the natural tendency
> > is to check that invalid value using (!dp->bridge_num). Latest example
> > can be seen in commit 1bec0f05062c ("net: dsa: fix bridge_num not
> > getting cleared after ports leaving the bridge").
> > 
> > Convert the existing users to assume that dp->bridge_num == 0 is the
> > encoding for invalid, and valid bridge numbers start from 1.
> > 
> > Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> > ---
> 
> Reviewed-by: Alvin Šipraga <alsi@...g-olufsen.dk>

Thanks for the review.

> Small remark inline.
> 
> > -int dsa_bridge_num_get(const struct net_device *bridge_dev, int max)
> > +unsigned int dsa_bridge_num_get(const struct net_device *bridge_dev, int max)
> >   {
> > -	int bridge_num = dsa_bridge_num_find(bridge_dev);
> > +	unsigned int bridge_num = dsa_bridge_num_find(bridge_dev);
> >   
> > -	if (bridge_num < 0) {
> > +	if (!bridge_num) {
> >   		/* First port that offloads TX forwarding for this bridge */
> 
> Perhaps you want to update this comment in patch 2/6, since bridge_num 
> is no longer just about TX forwarding offload.
> 
> > -		bridge_num = find_first_zero_bit(&dsa_fwd_offloading_bridges,
> > -						 DSA_MAX_NUM_OFFLOADING_BRIDGES);
> > +		bridge_num = find_next_zero_bit(&dsa_fwd_offloading_bridges,
> > +						DSA_MAX_NUM_OFFLOADING_BRIDGES,
> > +						1);

I will update this comment in patch 2 to say "First port that requests
FDB isolation or TX forwarding offload for this bridge". Sounds ok?