netdev - Re: [PATCH 1/2] r6040: fix multicast operations

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Date:	Wed, 27 Oct 2010 09:19:03 +0800
From:	Shawn Lin <shawn@....com.tw>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Florian Fainelli <florian@...nwrt.org>, netdev@...r.kernel.org,
	Marc Leclerc <marc-leclerc@...naturealpha.com>,
	Albert Chen <albert.chen@....com.tw>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH 1/2] r6040: fix multicast operations

On Tue, 2010-10-26 at 15:02 +0100, Ben Hutchings wrote:
> On Thu, Oct 21, 2010 at 04:27:34PM +0800, Shawn Lin wrote:
> [...]
> > > > +	/* Use internal multicast address registers
> > > > +	 * if the number of multicast addresses is not greater than MCAST_MAX.
> > > > +	 */
> > > > +	else if (netdev_mc_empty(dev)) {
> > > > +		for (i = 0; i < MCAST_MAX ; i++) {
> > > > +			iowrite16(0, ioaddr + MID_1L + 8 * i);
> > > > +			iowrite16(0, ioaddr + MID_1M + 8 * i);
> > > > +			iowrite16(0, ioaddr + MID_1H + 8 * i);
> > > > +		}
> > > > +	} else if (netdev_mc_count(dev) <= MCAST_MAX) {
> > > > +		i = 0;
> > > > +		netdev_for_each_mc_addr(ha, dev) {
> > > > +			adrp = (u16 *) ha->addr;
> > > > +			iowrite16(adrp[0], ioaddr + MID_1L + 8 * i);
> > > > +			iowrite16(adrp[1], ioaddr + MID_1M + 8 * i);
> > > > +			iowrite16(adrp[2], ioaddr + MID_1H + 8 * i);
> > > > +			i++;
> > > > +		}
> > > 
> > > What about the unused exact match entries?  And why is the empty case
> > > special?
> > 
> > Unused exact match entries? I am not sure which entries are you
> > mentioned.
> 
> If there are 1 or 2 addresses in the multicast list then some of the
> exact match entries will be used and some will not.  But the loop
> above does not clear the unused entries.
> 

Yes, you are right.

> [...]
> > 2) if (netdev_mc_count(dev) <= 3)
> > There are two hardware features could be used to filter multicast
> > frames:
> [...]
> > 3) if (netdev_mc_empty(dev))
> > because we masked the multicast hash table flag before examine all
> > conditions, we only need to clear the addresses in the three
> > MAC/Multicast registers.
> [...]
> 
> But why is this so different from the case of 1-3 addresses?  I would
> write these two cases as:
> 
> else if (netdev_mc_count(dev) <= MCAST_MAX) {
> 	i = 0;
> 	netdev_for_each_mc_addr(ha, dev) {
> 		adrp = (u16 *) ha->addr;
> 		iowrite16(adrp[0], ioaddr + MID_1L + 8 * i);
> 		iowrite16(adrp[1], ioaddr + MID_1M + 8 * i);
> 		iowrite16(adrp[2], ioaddr + MID_1H + 8 * i);
> 		i++;
> 	}
> 	while (i < MCAST_MAX) {
> 		iowrite16(0, ioaddr + MID_1L + 8 * i);
> 		iowrite16(0, ioaddr + MID_1M + 8 * i);
> 		iowrite16(0, ioaddr + MID_1H + 8 * i);
> 		i++;
> 	}
> } 
> 
> Ben.
> 

Thanks.

I will fix the issues you mentioned and resubmit the code.

--
Regards,

Shawn Lin


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