Subject: [PATCH 1/1] of: introduce helper to manage boolean

From: [email-masked] (Grant Likely)
Date: Thu, 08 Mar 2012 18:44:41 -0700

On Tue,  7 Feb 2012 05:13:48 +0100, Jean-Christophe PLAGNIOL-VILLARD <[email-masked]> wrote:
> of_property_read_bool
> 
> Search for a property in a device node and read a 32-bit value from
> it. Returns 0 if <0> or if the property does not exist, 1 if <1> or none.
> 
> this will allow to disable a boolean
> 
> is-ok;          => true
> is-ok = <1>;    => true
> is-ok = <0>;    => false
> 
> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <[email-masked]>
> Cc: devicetree-discuss at lists.ozlabs.org
> ---
> Hi,
> 
> 	if this is ok I'll rebase my mtd and i2c patch to use it
> 
> Best Regards,
> J.
>  drivers/of/base.c  |   30 ++++++++++++++++++++++++++++++
>  include/linux/of.h |    8 ++++++++
>  2 files changed, 38 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 133908a..a0eaf08 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -686,6 +686,36 @@ int of_property_read_u64(const struct device_node *np, const char *propname,
>  EXPORT_SYMBOL_GPL(of_property_read_u64);
>  
>  /**
> + * of_property_read_bool - Find and read a boolean from a property
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + *
> + * Search for a property in a device node and read a 32-bit value from
> + * it. Returns 0 if <0> or if the property does not exist, 1 if <1> or none.
> + *
> + * is-ok;	=> true
> + * is-ok = <1>;	=> true
> + * is-ok = <0>;	=> false
> + */
> +int of_property_read_bool(const struct device_node *np, const char *propname)
> +{
> +	u32 reg;
> +	int ret = of_property_read_u32(np, propname, &reg);
> +
> +	switch (ret) {
> +	case -EINVAL:
> +		return false;
> +	case -ENODATA:
> +		return true;
> +	case 0:
> +		return reg == 1;

Ugh.  so any value other than 1 returns false?  I think that will surprise
most people.

I don't like this api or binding.  If it is a bool property, then why isn't
simply testing for the property existance sufficient?

g.