netdev - Re: [RFC 1/2] genetlink: introduce pre_doit/post

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Message-ID: <1285887352.5137.34.camel@jlt3.sipsolutions.net>
Date:	Fri, 01 Oct 2010 00:55:52 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Julian Calaby <julian.calaby@...il.com>
Cc:	netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
	tgraf@...g.ch
Subject: Re: [RFC 1/2] genetlink: introduce pre_doit/post_doit hooks

On Fri, 2010-10-01 at 08:51 +1000, Julian Calaby wrote:

> > Come to think of it -- I could get away with a single pointer, since, if
> > both are assigned,
> >
> > user_ptr[0] == wiphy_to_rdev(((netdev *)user_ptr[1])->ieee80211_ptr->wiphy)
> >
> > but that's a lot of pointy things, and some functions only have the rdev
> > so it gets more complex. I think allowing two private pointers is a
> > decent compromise.
> 
> Come to think of it -- if someone wanted to have a massive structure
> with 10 pointers and a set of random data structures, then they could
> easily create their priv struct and assign it to user_ptr[0], hence
> rendering my argument null and void.

Oh, well, I thought your argument was that it was arbitrary and not
really necessary :-)

Also, this rather cheap, it just needs a bit more stack space in a place
that isn't typically deeply nested. So if some protocol came around and
needed three pointers, I'd probably advocate just bumping it to three.
At some point I might draw a line (10 is probably too much).

But you're right, of course, they can just use the first one and put
something dynamically allocated into that, if really needed.

johannes

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