From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Subject: Re: [PATCH V3 1/3] mmc: Add size for caller in init+register
Date: Wed, 29 May 2013 16:19:28 +0200
Message-ID: <201305291619.28396.arnd@arndb.de>
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To: Ulf Hansson <ulf.hansson-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christian Daudt <csd-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>, Jerry Huang <Chang-Ming.Huang-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, Wei WANG <wei_wang-kXabqFNEczNtrwSWzY7KCg@public.gmane.org>, matt.porter-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, Kevin Liu <kliu5-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>, Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Viresh Kumar <viresh.kumar-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Chris Ball <cjb-2X9k7bc8m7Mdnm+yROfE0A@public.gmane.org>, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>, Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>, Bill Pemberton <wfp5p-4Ng6DfrEGID2fBVCVOL8/A@public.gmane.org>, Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>, Anton Vorontsov <avorontsov-hkdhdckH98+B+jHODAdFcQ@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, linux-mmc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Guennadi Liakhovetski <g.liakhovetski-Mmb7MZpHnFY@public.gmane.org>
List-Id: devicetree@vger.kernel.org

On Wednesday 29 May 2013, Ulf Hansson wrote:
> > diff --git a/drivers/mmc/host/sdhci-pltfm.h b/drivers/mmc/host/sdhci-pltfm.h
> > index 1210ed1..ed4a85d 100644
> > --- a/drivers/mmc/host/sdhci-pltfm.h
> > +++ b/drivers/mmc/host/sdhci-pltfm.h
> > @@ -27,6 +27,8 @@ struct sdhci_pltfm_host {
> >         /* migrate from sdhci_of_host */
> >         unsigned int clock;
> >         u16 xfer_mode_shadow;
> > +
> > +       unsigned long private[0] ____cacheline_aligned;
> 
> Why do you need this to be "____cacheline_aligned"?

This is common practice for additional members in data structures
like this. The reason is that we append a structure which
may have larger alignment requirements than 'unsigned long'.

The kmalloc function generally returns a cache line aligned
object, so this provides the same alignment that we get
with a separate allocation.

	Arnd