From: Jason Lunz <lunz@falooley.org>
To: netdev@oss.sgi.com
Subject: Re: double-check me?
Date: Sun, 17 Aug 2003 21:34:22 +0000 (UTC) [thread overview]
Message-ID: <slrnbjvt6q.u4n.lunz@orr.homenet> (raw)
In-Reply-To: 3F3FBF50.8070207@pobox.com
jgarzik@pobox.com said:
> if (sizeof_priv)
> dev->priv = (void *) (((long)(dev + 1) + 31) & ~31);
>
>
> Now... shouldn't that last line of code be "dev + 1 + sizeof(*dev)" ?
are you missing that the "dev + 1" pointer arithmetic is already adding
sizeof(*dev) to dev, rather than just 1 byte? "(dev + 1)" is a pointer
to the private area after the actual struct net_device, and
"((long)(dev + 1) + 31)" adds 31 bytes of padding. The final "& ~31"
chops off any excess padding from the 31 that was added and actually
aligns the pointer.
Seems right to me, but I'm not used to playing alignment tricks.
Jason
prev parent reply other threads:[~2003-08-17 21:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-17 17:45 double-check me? Jeff Garzik
2003-08-17 20:58 ` Krzysztof Halasa
2003-08-17 22:31 ` Jeff Garzik
2003-08-18 14:38 ` Jason Lunz
2003-08-18 14:41 ` Jeff Garzik
2003-08-17 21:34 ` Jason Lunz [this message]
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