linux-kernel - Re: [PATCH 2/5] mfd: arizona: Fix and factor out read of device tree GPIOs

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Message-ID: <20140321154400.GF1665@opensource.wolfsonmicro.com>
Date:	Fri, 21 Mar 2014 15:44:00 +0000
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	broonie@...nel.org, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, rob@...dley.net, sameo@...ux.intel.com,
	lgirdwood@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] mfd: arizona: Fix and factor out read of device
	tree GPIOs

On Fri, Mar 21, 2014 at 10:52:18AM +0000, Lee Jones wrote:
> On Wed, 19 Mar 2014, Charles Keepax wrote:
> 
> > On non-DT systems with device tree built in the current device tree GPIO
> > reads will overwrite the pdata with zero when they fail. This patch
> > factors out the reading of GPIOs for the Arizona devices into a helper
> > function, and ensures that the pdata version will be preserved if the
> > device tree read fails.
> > 
> > Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> > ---
> >  drivers/mfd/arizona-core.c       |   33 ++++++++++++++++++++++++---------
> >  include/linux/mfd/arizona/core.h |    3 +++
> >  2 files changed, 27 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/mfd/arizona-core.c b/drivers/mfd/arizona-core.c
> > index a45aab9..333621e 100644
> > --- a/drivers/mfd/arizona-core.c
> > +++ b/drivers/mfd/arizona-core.c
> > @@ -512,19 +512,34 @@ int arizona_of_get_type(struct device *dev)
> >  }
> >  EXPORT_SYMBOL_GPL(arizona_of_get_type);
> >  
> > +int arizona_of_get_named_gpio(struct arizona *arizona, const char *prop,
> > +			      bool mandatory, int *gpio)
> > +{
> > +	int ret;
> > +
> > +	ret = of_get_named_gpio(arizona->dev->of_node, prop, 0);
> > +	if (ret >= 0) {
> > +		*gpio = ret;
> > +		return ret;
> > +	}
> > +
> > +	/* Warn if GPIO is mandatory and not specified */
> > +	if (mandatory && *gpio <= 0)
> > +		dev_err(arizona->dev,
> > +				"Mandatory DT gpio %s missing/malformed: %d\n",
> > +				prop, ret);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(arizona_of_get_named_gpio);
> > +
> >  static int arizona_of_get_core_pdata(struct arizona *arizona)
> >  {
> > +	struct arizona_pdata *pdata = &arizona->pdata;
> >  	int ret, i;
> >  
> > -	arizona->pdata.reset = of_get_named_gpio(arizona->dev->of_node,
> > -						 "wlf,reset", 0);
> > -	if (arizona->pdata.reset < 0)
> > -		arizona->pdata.reset = 0;
> > -
> > -	arizona->pdata.ldoena = of_get_named_gpio(arizona->dev->of_node,
> > -						  "wlf,ldoena", 0);
> > -	if (arizona->pdata.ldoena < 0)
> > -		arizona->pdata.ldoena = 0;
> > +	arizona_of_get_named_gpio(arizona, "wlf,reset", true, &pdata->reset);
> > +	arizona_of_get_named_gpio(arizona, "wlf,ldoena", true, &pdata->ldoena);
> >  
> >  	ret = of_property_read_u32_array(arizona->dev->of_node,
> >  					 "wlf,gpio-defaults",
> 
> This doesn't look correct to me at all. Have you tested it in the DT
> and !DT case? By the looks of it arizona_of_get_core_pdata() is only
> called if no platform data is present. Yet you are dereferencing it
> here without allocated any memory.

The pdata struct is contained within the arizona one so there is
no need to allocate memory for it.

> 
> So how were any platform data passed variables being overwritten in
> the first place?

Ah good point this is not called if the pdata exists, I will
update the commit message.

Thanks,
Charles
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