linux-kernel - Re: [PATCH 13/18] ARM: at91/rtc-at91sam9: pass the GPBR to use via ressources

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Date:	Mon, 20 Feb 2012 07:36:21 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Ryan Mallon <rmallon@...il.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 13/18] ARM: at91/rtc-at91sam9: pass the GPBR to use via
	ressources

On Mon, Feb 20, 2012 at 02:20:10AM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 11:43 Mon 20 Feb     , Ryan Mallon wrote:
> > On 18/02/12 04:50, Nicolas Ferre wrote:
> > 
> > > From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
> > > 
> > > The GPBR registers are used for storing RTC values. The GPBR registers
> > > to use are now provided using standard resource entry. The array is
> > > filled in SoC specific code.
> > > rtc-at91sam9 RTT as RTC driver is modified to retrieve this information.
> > > 
> > > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
> > > Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
> > > ---
> > >  arch/arm/mach-at91/at91sam9260_devices.c      |   10 +++++++-
> > >  arch/arm/mach-at91/at91sam9261_devices.c      |    8 ++++++-
> > >  arch/arm/mach-at91/at91sam9263_devices.c      |   16 +++++++++++--
> > >  arch/arm/mach-at91/at91sam9g45_devices.c      |    8 ++++++-
> > >  arch/arm/mach-at91/at91sam9rl_devices.c       |    8 ++++++-
> > >  arch/arm/mach-at91/include/mach/at91sam9260.h |    5 +--
> > >  arch/arm/mach-at91/include/mach/at91sam9261.h |    5 +--
> > >  arch/arm/mach-at91/include/mach/at91sam9263.h |    5 +--
> > >  arch/arm/mach-at91/include/mach/at91sam9g45.h |    5 +--
> > >  arch/arm/mach-at91/include/mach/at91sam9rl.h  |    2 +-
> > >  drivers/rtc/rtc-at91sam9.c                    |   29 +++++++++++++++++++++---
> > >  11 files changed, 76 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/arch/arm/mach-at91/at91sam9260_devices.c b/arch/arm/mach-at91/at91sam9260_devices.c
> > > index 2071017..ae2b648 100644
> > > --- a/arch/arm/mach-at91/at91sam9260_devices.c
> > > +++ b/arch/arm/mach-at91/at91sam9260_devices.c
> > > @@ -718,14 +718,16 @@ static struct resource rtt_resources[] = {
> > >  		.start	= AT91SAM9260_BASE_RTT,
> > >  		.end	= AT91SAM9260_BASE_RTT + SZ_16 - 1,
> > >  		.flags	= IORESOURCE_MEM,
> > > -	}
> > > +	}, {
> > > +		.flags	= IORESOURCE_MEM,
> > > +	},
> > >  };
> > >  
> > >  static struct platform_device at91sam9260_rtt_device = {
> > >  	.name		= "at91_rtt",
> > >  	.id		= 0,
> > >  	.resource	= rtt_resources,
> > > -	.num_resources	= ARRAY_SIZE(rtt_resources),
> > > +	.num_resources	= 1,
> > 
> > 
> > Why this change? The device has two resources, and the rtc driver
> > request both of them, so why are you saying there is only one resource
> > here. It either needs to be changed back to use ARRAY_SIZE, or needs a
> > comment explaining what magic is in use.
> because the number of resources depends on the user of rtt
> we must not hardcode the GPBR reg as this resource will be present only if the
> rtc-at91sam9 is enabled

Better would be to leave .num_resources uninitalized and set that
appropriately elsewhere when you make the decision whether GPBR is
present or not.  That may help to avoid people trying to "fix" this
for you via static checking tools.

As Ryan mentions, a comment in the code would be a good idea too.
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