Date: Tue, 23 Nov 2010 09:57:51 -0800
From: "Luis R. Rodriguez" <lrodriguez@atheros.com>
To: Arnaud Lacombe <lacombar@gmail.com>
CC: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	Luis Rodriguez <Luis.Rodriguez@Atheros.com>
Subject: Re: [PATCH 28/44] compat: avoid using `#include_next' directive in
 compat headers
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On Mon, Nov 22, 2010 at 07:22:28PM -0800, Luis R. Rodriguez wrote:
> On Mon, Nov 22, 2010 at 6:40 PM, Arnaud Lacombe <lacombar@gmail.com> wrote:
> > Hi,
> >
> > On Mon, Nov 22, 2010 at 9:32 PM, Luis R. Rodriguez
> > <lrodriguez@atheros.com> wrote:
> >> On Mon, Nov 22, 2010 at 6:19 PM, Arnaud Lacombe <lacombar@gmail.com> wrote:
> >>> Hi,
> >>>
> >>> On Mon, Nov 22, 2010 at 1:09 PM, Luis R. Rodriguez
> >>> <lrodriguez@atheros.com> wrote:
> >>>> On Sun, Nov 21, 2010 at 5:36 PM, Arnaud Lacombe <lacombar@gmail.com> wrote:
> >>>>> [...]
> >>>>> The compat headers should be at the end of the include list, so that
> >>>>> the kernel headers get included first, and the compat one will only be
> >>>>> when the kernel does not provide the header. This is the only sane way
> >>>>> to override kernel provided stuff. That said, there is certainly a
> >>>>> use-case I missed.
> >>>>
> >>>> Agreed, but you are missing the purpose of the trick used here.
> >>> certainly :)
> >>>
> >>>> The
> >>>> purpose of the include_next was so that we can name our own
> >>>> <linux/pm_qos_params.h> which is part of compat and these directories
> >>>> *will* get a priority over the kernel's so that way we can avoid
> >>>> ifdef'ing all includes for the same file on the upstream code.
> >>> I'm not sure to get what you mean by "we can avoid ifdef'ing all
> >>> includes for the same file on the upstream code", can you details ?
> >>
> >> Ah, that's right, you don't see or use compat-wireless likely. Ok, so
> >> what we do for backporting the 802.11 subsystem, Bluetooth and some
> >> Ethernet drivers is we take the stock upstream files, stuff them into
> >> a new directory, and then apply a series of patches to them to get the
> >> files to properly compile. The patches address all things that was not
> >> possible to backport through compat.git. Header file changes is one of
> >> the typical things we run into. If a new header file is added to newer
> >> kernels we can play a hack for older kernels and leave the code intact
> >> and introduce our own include/linux/foo.h through compat by prefering
> >> the local path over the kernel's path. If we're on newer kernels
> >> though include_next will go on the search path and find the kernel's
> >> own header file.
> >>
> > Is there any reason you want the compat's include directory to be
> > *before* the kernel include directory ?
> 
> Hm, yeah but I forget why. It'll come to me.

Ah, OK so its because we provide our own mac80211.h, and new cfg80211.h

  Luis