Subject: Re: [PATCH] 3c59x: sparse warning fix

From: Stephen Hemminger <[email-masked]>
Date: Wed, 5 Sep 2007 23:46:18 +0100

On Wed, 05 Sep 2007 09:57:05 -0700
Joe Perches <[email-masked]> wrote:

> On Wed, 2007-09-05 at 15:23 +0100, Stephen Hemminger wrote:
> > --- a/drivers/net/3c59x.c	2007-09-05 15:15:16.000000000 +0100
> > +++ b/drivers/net/3c59x.c	2007-09-05 15:16:29.000000000 +0100
> > @@ -1122,7 +1122,7 @@ static int __devinit vortex_probe1(struc
> >  					   + sizeof(struct boom_tx_desc) * TX_RING_SIZE,
> >  					   &vp->rx_ring_dma);
> >  	retval = -ENOMEM;
> > -	if (vp->rx_ring == 0)
> > +	if (!vp->rx_ring)
> >  		goto free_region;
> >  
> >  	vp->tx_ring = (struct boom_tx_desc *)(vp->rx_ring + RX_RING_SIZE);
> > @@ -2476,7 +2476,8 @@ boomerang_rx(struct net_device *dev)
> >  
> >  			/* Check if the packet is long enough to just accept without
> >  			   copying to a properly sized skbuff. */
> > -			if (pkt_len < rx_copybreak && (skb = dev_alloc_skb(pkt_len + 2)) != 0) {
> > +			if (pkt_len < rx_copybreak &&
> > +			    (skb = dev_alloc_skb(pkt_len + 2)) ) {
> >  				skb_reserve(skb, 2);	/* Align IP on 16 byte boundaries */
> >  				pci_dma_sync_single_for_cpu(VORTEX_PCI(vp), dma, PKT_BUF_SZ, PCI_DMA_FROMDEVICE);
> >  				/* 'skb_put()' points to the start of sk_buff data area. */
> 
> Shouldn't this be:
> 
> 	if (pkt_len < rx_copybreak) {
> 		skb = dev_alloc_skb(pkt_len + 2);
> 		if (!skb) {
> 			bad_news! (like the refill rx ring buffers block)
> 		}

No, the existing code path does the right thing, and if skb can't be allocated
it just reuses the existing one. Having a single error recovery path (for out of
memory) is preferable to two paths.