Re: [RFC 1/2] genetlink: introduce pre_doit/post_doit hooks

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2010-10-01 at 00:47 +0200, Johannes Berg wrote:
> On Fri, 2010-10-01 at 00:44 +0200, Johannes Berg wrote:
> > On Fri, 2010-10-01 at 08:41 +1000, Julian Calaby wrote:
> > 
> > > >  d) include two private pointers in each info
> > > >    struct passed between all these operations
> > > >    including doit(). (It's two because I'll
> > > >    need two in nl80211 -- can be extended.)
> > > 
> > > Stupid question:
> > > 
> > > Why not have a priv struct rather than an arbitrary array of two pointers?
> > 
> > It'd have to be dynamically allocated, and the "arbitrary" array of two
> > pointers can be on the stack.
> 
> Maybe I should elaborate -- a priv struct basically means just a single
> pointer, and then I'd have to allocate something to hold two pointers in
> nl80211 and assign it to that single pointer.

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.

johannes