Re: [CFT] 2.6.x experimental net driver updates

viro_at_parcelfarce.linux.theplanet.co.uk
Date: 11/20/03

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    Date:	Thu, 20 Nov 2003 05:47:29 +0000
To: Jeff Garzik <jgarzik@pobox.com>

    On Thu, Nov 20, 2003 at 12:23:44AM -0500, Jeff Garzik wrote:
    > viro@parcelfarce.linux.theplanet.co.uk wrote:
    > >On Wed, Nov 19, 2003 at 12:33:08PM -0500, Jeff Garzik wrote:
    > >
    > >>Ok, Al Viro's net driver refcounting work is pretty much complete, and
    > >
    > >
    > >The hell it is. We are through with legacy probes, we are through with
    > >init_etherdev(), we are practically through with static struct net_device.
    >
    > hehe :) I don't mean to suggest that all is clean and pure :)
    >
    >
    > >However, we still have weird allocators (I've got almost all of them
    > >done by now, will submit in the next batch) and we still have struct
    > >net_device embedded as a field of other structures in several drivers.
    >
    > Some of that will be interesting. ns83820 for example embedded
    > net_device on purpose... Ben seemed to think at the time it gave him
    > some speed, a few less pointer derefs and such.

    That's fine, but 83820 should be doing that the other way round.

    Note that for objects allocated by alloc_netdev() we have
            (char*) dev->priv == (char *)dev + const
    and constant can be found at compile time _if_ we pad in front of
    net_device and add a pointer to allocated block into net_device.

    So we can have exactly the same structure (modulo padding) and no extra
    dereferencing. All we need is inlined void *net_priv(struct net_device *);

    That, BTW, would be a win for other drivers using alloc_...() and not
    reassigning ->priv (i.e. majority of those beasts).
    -
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