Re: double-check me?

[Krzysztof Halasa <khc@pm.waw.pl>]

Jeff Garzik <jgarzik@pobox.com> writes:

> Maybe you guys can spot something I'm missing here.  alloc_netdev is
> supposed to guarantee that dev->priv is aligned by 32 bytes:
> 
>          struct net_device *dev;
> 
>          if (sizeof_priv)
>                  dev->priv = (void *) (((long)(dev + 1) + 31) & ~31);
> 
> 
> Now... shouldn't that last line of code be "dev + 1 + sizeof(*dev)" ?
> 
> It seems to work 2.[456] for a long time, so I am doubting
> myself... surely it would have caused memory corruption or something
> by now if I have really found a bug.

Looks ok... not very readable, though.

dev + 1 = ((u8*)dev) + sizeof(dev) = pointer to end of net_device struct.

(X + 31) & ~31 makes sure X is 32-bytes aligned (0-31 bytes are added).
Hope the alloc_size has enough space for this.

31 should be better 0x1F I think.

I also like sizeof(struct net_device) more than sizeof(*dev).

Why do you want "+ 1" if you add sizeof(*dev)?
-- 
Krzysztof Halasa
Network Administrator