netdev - Re: [PATCH net-2.6.24] introduce MAC_FMT/MAC

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Message-Id: <1188212049.6756.18.camel@johannes.berg>
Date:	Mon, 27 Aug 2007 12:54:09 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Joe Perches <joe@...ches.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-2.6.24] introduce MAC_FMT/MAC_ARG

On Sat, 2007-08-25 at 17:09 -0700, Joe Perches wrote:
> 
> @@ -747,22 +741,15 @@ static int ariadne_rx(struct net_device *dev)
>             skb_copy_to_linear_data(skb, (char *)priv->rx_buff[entry],
> pkt_len);
>             skb->protocol=eth_type_trans(skb,dev);
>  #if 0
>  (int)skb->len);
> +{
> +           printk(KERN_DEBUG "RX pkt type 0x%04x"
> +                  " from " MAC_FMT " to " MAC_FMT
> +                  " data 0x%08x len %d\n",
> +                  ((u_short *)skb->data)[6],
> +                  MAC_ARG(((u_char *)skb->data)+6),
> +                  MAC_ARG((u_char *)skb->data),
> +                  (int)skb->data, (int)skb->len);
> +}
>  #endif 

You could drop the braces since there are no variables there any more.

Thanks for this patch though, I'd have done it otherwise.

I was rereading your original conversion and noticed that it is now
trivial to make the kernel smaller like you originally wanted by doing
something like this

-- define this function somewhere --
print_mac(u8 *mac, char *buf)
{
	sprintf(buf, "%02x:...", mac[0], mac[1], ...);
}
EXPORT_SYMBOL(print_mac)

-- change macros to --
#define MAC_FMT "%s"
#define MAC_ARG(a) ({char __buf[18]; print_mac(a, buf); __buf})

I'm not sure we'd want that, but at the time you said it made the kernel
significantly smaller and I doubt there's a performance problem with it
(who prints mac addresses regularly?)

johannes

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