Date:	Thu, 18 Sep 2014 07:58:17 +0000
From:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>
To:	Pankaj Dubey <pankaj.dubey@...sung.com>,
	"Aisheng.Dong@...escale.com" <Aisheng.Dong@...escale.com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kgene.kim@...sung.com" <kgene.kim@...sung.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"arnd@...db.de" <arnd@...db.de>,
	"naushad@...sung.com" <naushad@...sung.com>,
	"tomasz.figa@...il.com" <tomasz.figa@...il.com>,
	"joshi@...sung.com" <joshi@...sung.com>,
	"thomas.ab@...sung.com" <thomas.ab@...sung.com>,
	"vikas.sajjan@...sung.com" <vikas.sajjan@...sung.com>,
	"chow.kim@...sung.com" <chow.kim@...sung.com>,
	"lee.jones@...aro.org" <lee.jones@...aro.org>,
	"'Boris BREZILLON'" <boris.brezillon@...e-electrons.com>,
	'Geert Uytterhoeven' <geert+renesas@...der.be>,
	'Stephen Warren' <swarren@...dia.com>
Subject: RE: [PATCH v3] mfd: syscon: Decouple syscon interface from platform
 devices

Hi,

[...]
> > please see regmap_get_val_endian called in regmap_init function.
> > static enum regmap_endian regmap_get_val_endian(struct device *dev,
> >                                         const struct regmap_bus *bus,
> >                                         const struct regmap_config
> *config) {
> >         struct device_node *np = dev->of_node;
> >         enum regmap_endian endian;
> > ...
> > }
> > It will crash at the first line of dev->of_node if dev is NULL.
> >
> > Can you check if you're using the same code as mine?
> 
> No, it's not same.
> My bad that I was not using linux-next for testing this patch.
> We tested on kgene/for-next where these changes still have not come.
> Just now I checked linux-next and found that it will crash at first line of
> "regmap_get_val_endian" as there is no check for NULL on dev.
> 
> I checked git history of regmap.c file and found recently this file has been
> modified
> for adding DT endianness binding support. Following are set of patches gone
> for this
> 
> cf673fb regmap: Split regmap_get_endian() in two functions
> 5844a8b regmap: Fix handling of volatile registers for format_write() chips
> 45e1a27 regmap: of_regmap_get_endian() cleanup
> ba1b53f regmap: Fix DT endianess parsing logic
> d647c19 regmap: add DT endianness binding support.
> 
> I think there should have been a check for NULL on "dev" in
> "regmap_get_val_endian", so that if dev pointer exist then only it makes
> sense to get
> endianness property from DT.
> 
> I will suggest following fix in regmap.c for this. With following fix I
> tested it and it works well
> on linux-next also. So if you can confirm following fix is working for you
> then I can post this
> patch.
> 
> --------------------------------------------
> Subject: [PATCH] regmap: fix NULL pointer dereference in
>  regmap_get_val_endian
> 
> Recent commits for getting reg endianess causing NULL pointer
> dereference if dev is passed NULL in regmap_init_mmio. This patch
> fixes this issue, and allows to parse reg endianess only if dev
> and dev->of_node exist.
> 

Another question:

Then the regmap core cannot deal with the following issue:
Like the patch adding the endianness support for syscon:
    [PATCH] mfd: syscon: binding: Add syscon endianness support.

So here just register one dummy syscon device is a good choice I do
think.
:)


Thanks,

BRs
Xiubo



> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
>  drivers/base/regmap/regmap.c |   23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index f2281af..455a877 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -477,7 +477,7 @@ static enum regmap_endian regmap_get_val_endian(struct
> device *dev,
>  					const struct regmap_bus *bus,
>  					const struct regmap_config *config)
>  {
> -	struct device_node *np = dev->of_node;
> +	struct device_node *np;
>  	enum regmap_endian endian;
> 
>  	/* Retrieve the endianness specification from the regmap config */
> @@ -487,15 +487,20 @@ static enum regmap_endian regmap_get_val_endian(struct
> device *dev,
>  	if (endian != REGMAP_ENDIAN_DEFAULT)
>  		return endian;
> 
> -	/* Parse the device's DT node for an endianness specification */
> -	if (of_property_read_bool(np, "big-endian"))
> -		endian = REGMAP_ENDIAN_BIG;
> -	else if (of_property_read_bool(np, "little-endian"))
> -		endian = REGMAP_ENDIAN_LITTLE;
> +	/* If the dev and dev->of_node exist try to get endianness from DT
> */
> +	if (dev && dev->of_node) {
> +		np = dev->of_node;
> 
> -	/* If the endianness was specified in DT, use that */
> -	if (endian != REGMAP_ENDIAN_DEFAULT)
> -		return endian;
> +		/* Parse the device's DT node for an endianness
> specification */
> +		if (of_property_read_bool(np, "big-endian"))
> +			endian = REGMAP_ENDIAN_BIG;
> +		else if (of_property_read_bool(np, "little-endian"))
> +			endian = REGMAP_ENDIAN_LITTLE;
> +
> +		/* If the endianness was specified in DT, use that */
> +		if (endian != REGMAP_ENDIAN_DEFAULT)
> +			return endian;
> +	}
> 
>  	/* Retrieve the endianness specification from the bus config */
>  	if (bus && bus->val_format_endian_default)
> --
> 
> Thanks,
> Pankaj Dubey
> 
> > Regards
> > Dong Aisheng
> >
> > >
> > > Thanks,
> > > Pankaj Dubey
> > >
> > > > Regards
> > > > Dong Aisheng
> > > >
> > > > >
> > > > >
> > > > > _______________________________________________
> > > > > linux-arm-kernel mailing list
> > > > > linux-arm-kernel@...ts.infradead.org
> > > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > >

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