[PATCH 03/10] net/fec: add mac field into platform data and consolidate fec_get_mac

Hello Shawn,

On Thu, Dec 30, 2010 at 10:12:44AM +0800, Shawn Guo wrote:

On Wed, Dec 29, 2010 at 01:42:21PM +0100, Uwe Kleine-K?nig wrote:

quoted

On Wed, Dec 29, 2010 at 07:58:09PM +0800, Shawn Guo wrote:

quoted

On Wed, Dec 29, 2010 at 11:31:38AM +0100, Uwe Kleine-K?nig wrote:

quoted

On Wed, Dec 29, 2010 at 06:05:21PM +0800, Shawn Guo wrote:

quoted

On Wed, Dec 29, 2010 at 08:53:30AM +0200, Baruch Siach wrote:
	if (iap == fec_mac_default)
		dev->dev_addr[ETH_ALEN-1] = fec_mac_default[ETH_ALEN-1] + fep->pdev->id;

Can this overflow?  (I didn't check the code, so my concern might be
completely stupid here.)

No. dev->dev_addr points to netdev_hw_addr->addr, which is a 32 bytes array.

I didn't mean an out-of-bound access, but what is if
fec_mac_default[ETH_ALEN-1] is 0xff and you add 1?  Does that result in
0x100 or 0?  What if id is <0?  For big ids you might even handle a
carry to indixes <ETH_ALEN-2.

First of all, all my patch did is changing fep->index to,
fep->pdev->id, which should not bring any problem you are concerned.

Secondly, I do not understand how the overflow on 
fec_mac_default[ETH_ALEN-1] can result in a carry on the next array
element. Here is what I'm seeing with fec_mac=00:04:9f:01:30:ff.

There is no automatic carry to the next array element.  I just wondered
how overflow should be handled ...
 

eth0      Link encap:Ethernet  HWaddr 00:04:9F:01:30:FF
eth1      Link encap:Ethernet  HWaddr 00:04:9F:01:30:00

If this is intended, it's totally OK for me.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |