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Re: [janitor] remove casts in drivers/net/arm/

To: "Randy.Dunlap" <rddunlap@xxxxxxxx>
Subject: Re: [janitor] remove casts in drivers/net/arm/
From: Jeff Garzik <jgarzik@xxxxxxxxx>
Date: Tue, 02 Mar 2004 14:07:36 -0500
Cc: rmk@xxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx
In-reply-to: <20040302110237.0f580736.rddunlap@xxxxxxxx>
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Randy.Dunlap wrote:
On Tue, 02 Mar 2004 13:54:36 -0500 Jeff Garzik wrote:

| Russell King wrote:
| > On Sun, Feb 29, 2004 at 02:34:36PM -0800, Randy.Dunlap wrote:
| > | >> drivers/net/arm/am79c961a.c | 18 +++++++++---------
| >> drivers/net/arm/ether1.c    |   18 +++++++++---------
| >> drivers/net/arm/ether3.c    |   18 +++++++++---------
| >> drivers/net/arm/etherh.c    |    4 ++--
| >> 4 files changed, 29 insertions(+), 29 deletions(-)
| > | > | > I think we should really consider using netdev_priv() in all these places
| > so the compiler knows that 'dev' and 'priv' are related.
| | | Good point.

I respectfully disagree, but if the maintainter won't merge
them as is, so be it.

I have trouble understanding why this:
        return (char *)dev + ((sizeof(struct net_device) + 31) & ~31);
is better than using a structure->field, i.e.,
        dev->priv

Can one of you enlighten me?


One is an additional pointer load and dereference, and one is a constant offset from the beginning of the dev structure, calculated at compile time. netdev_priv() provides the same results as dev->priv but at less cost.

        Jeff




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