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Date: Tue, 23 Feb 2010 07:59:53 +0100
From: Borislav Petkov <petkovbb@googlemail.com>
To: viresh kumar <viresh.linux@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: QUERY: Inclusion of header files in kernel header files
Message-ID: <20100223065953.GB32503@liondog.tnic>
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	viresh kumar <viresh.linux@gmail.com>, linux-kernel@vger.kernel.org
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From: viresh kumar <viresh.linux@gmail.com>
Date: Tue, Feb 23, 2010 at 12:13:35PM +0530

Hi,

> I have been through many kernel header files and have found that kernel header
> files at many places don't include other header files which they have
> dependency upon.
> 
> For example:
> <linux/amba/bus.h> uses struct device and struct resource and it doesn't
> include <linux/device.h> and <linux/resource.h> header files.
> 
> Now, whenever i try to include bus.h, i have to include device.h and resource.h.
> 
> Is this correct approach?
> 
> Again, if i include device.h and resource.h, they must be included before bus.h.

and this is the thing: all those other files which include
<linux/amba/bus.h> either include <linux/device.h> and
<linux/resource.h> directly or the last are being included indirectly
through other headers.

Baseline, struct device and struct resource's definitions have to be
available before <linux/amba/bus.h> is included. That's why you have to
include the bus.h header last.

> Now this will disturb the alphabetical ordering of including header files
> sometimes. (not in this example)

I don't think there's such thing as alphabetical header ordering and if
it were it would be rather dumb thing to do.

Hope this helps.

-- 
Regards/Gruss,
    Boris.
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