Re: [PATCH Resend V2] dt: add helper function to read u8 & u16 variables & arrays

[Rob Herring <robherring2@gmail.com>]

On 10/25/2012 11:20 PM, Viresh Kumar wrote:
> This adds following helper routines:
> - of_property_read_u8_array()
> - of_property_read_u16_array()
> - of_property_read_u8()
> - of_property_read_u16()
> 
> First two actually share most of the code with of_property_read_u32_array(), so
> the common part is taken out into a macro, which can be used by all three
> *_array() routines.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
> V1->V2:
> -----
> - Use typeof() in of_property_read_array() macro instead of passing type to it
> 
>  drivers/of/base.c  | 73 +++++++++++++++++++++++++++++++++++++++++++-----------
>  include/linux/of.h | 30 ++++++++++++++++++++++
>  2 files changed, 89 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index af3b22a..039e178 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -670,6 +670,64 @@ struct device_node *of_find_node_by_phandle(phandle handle)
>  }
>  EXPORT_SYMBOL(of_find_node_by_phandle);
>  
> +#define of_property_read_array(_np, _pname, _out, _sz)			\
> +	struct property *_prop = of_find_property(_np, _pname, NULL);	\
> +	const __be32 *_val;						\
> +									\
> +	if (!_prop)							\
> +		return -EINVAL;						\
> +	if (!_prop->value)						\
> +		return -ENODATA;					\
> +	if ((_sz * sizeof(*_out)) > _prop->length)			\
> +		return -EOVERFLOW;					\
> +									\
> +	_val = _prop->value;						\
> +	while (_sz--)							\
> +		*_out++ = (typeof(*_out))be32_to_cpup(_val++);		\

This will not work. You are incrementing _out by 1, 2, or 4 bytes, but
_val is always incremented by 4 bytes.

According to the dtc commit adding this feature, the values are packed:

With this patch the following property assignment:

    property = /bits/ 16 <0x1234 0x5678 0x0 0xffff>;

is equivalent to:

    property = <0x12345678 0x0000ffff>;


> +	return 0;
> +
> +/**
> + * of_property_read_u8_array - Find and read an array of u8 from a property.
> + *
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + * @out_value:	pointer to return value, modified only if return value is 0.
> + *

Missing sz

> + * Search for a property in a device node and read 8-bit value(s) from
> + * it. Returns 0 on success, -EINVAL if the property does not exist,
> + * -ENODATA if property does not have a value, and -EOVERFLOW if the
> + * property data isn't large enough.
> + *
> + * The out_value is modified only if a valid u8 value can be decoded.
> + */
> +int of_property_read_u8_array(const struct device_node *np,
> +			const char *propname, u8 *out_values, size_t sz)
> +{
> +	of_property_read_array(np, propname, out_values, sz);
> +}
> +EXPORT_SYMBOL_GPL(of_property_read_u8_array);
> +
> +/**
> + * of_property_read_u16_array - Find and read an array of u16 from a property.
> + *
> + * @np:		device node from which the property value is to be read.
> + * @propname:	name of the property to be searched.
> + * @out_value:	pointer to return value, modified only if return value is 0.
> + *

Ditto.

> + * Search for a property in a device node and read 16-bit value(s) from
> + * it. Returns 0 on success, -EINVAL if the property does not exist,
> + * -ENODATA if property does not have a value, and -EOVERFLOW if the
> + * property data isn't large enough.
> + *
> + * The out_value is modified only if a valid u16 value can be decoded.
> + */
> +int of_property_read_u16_array(const struct device_node *np,
> +			const char *propname, u16 *out_values, size_t sz)
> +{
> +	of_property_read_array(np, propname, out_values, sz);
> +}
> +EXPORT_SYMBOL_GPL(of_property_read_u16_array);
> +
>  /**
>   * of_property_read_u32_array - Find and read an array of 32 bit integers
>   * from a property.
> @@ -689,20 +747,7 @@ int of_property_read_u32_array(const struct device_node *np,
>  			       const char *propname, u32 *out_values,
>  			       size_t sz)
>  {
> -	struct property *prop = of_find_property(np, propname, NULL);
> -	const __be32 *val;
> -
> -	if (!prop)
> -		return -EINVAL;
> -	if (!prop->value)
> -		return -ENODATA;
> -	if ((sz * sizeof(*out_values)) > prop->length)
> -		return -EOVERFLOW;
> -
> -	val = prop->value;
> -	while (sz--)
> -		*out_values++ = be32_to_cpup(val++);
> -	return 0;
> +	of_property_read_array(np, propname, out_values, sz);
>  }
>  EXPORT_SYMBOL_GPL(of_property_read_u32_array);
>  
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 72843b7..e2d9b40 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -223,6 +223,10 @@ extern struct device_node *of_find_node_with_property(
>  extern struct property *of_find_property(const struct device_node *np,
>  					 const char *name,
>  					 int *lenp);
> +extern int of_property_read_u8_array(const struct device_node *np,
> +			const char *propname, u8 *out_values, size_t sz);
> +extern int of_property_read_u16_array(const struct device_node *np,
> +			const char *propname, u16 *out_values, size_t sz);
>  extern int of_property_read_u32_array(const struct device_node *np,
>  				      const char *propname,
>  				      u32 *out_values,
> @@ -357,6 +361,18 @@ static inline struct device_node *of_find_compatible_node(
>  	return NULL;
>  }
>  
> +static inline int of_property_read_u8_array(const struct device_node *np,
> +			const char *propname, u8 *out_values, size_t sz)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int of_property_read_u16_array(const struct device_node *np,
> +			const char *propname, u16 *out_values, size_t sz)
> +{
> +	return -ENOSYS;
> +}
> +
>  static inline int of_property_read_u32_array(const struct device_node *np,
>  					     const char *propname,
>  					     u32 *out_values, size_t sz)
> @@ -463,6 +479,20 @@ static inline bool of_property_read_bool(const struct device_node *np,
>  	return prop ? true : false;
>  }
>  
> +static inline int of_property_read_u8(const struct device_node *np,
> +				       const char *propname,
> +				       u8 *out_value)
> +{
> +	return of_property_read_u8_array(np, propname, out_value, 1);
> +}
> +
> +static inline int of_property_read_u16(const struct device_node *np,
> +				       const char *propname,
> +				       u16 *out_value)
> +{
> +	return of_property_read_u16_array(np, propname, out_value, 1);
> +}
> +
>  static inline int of_property_read_u32(const struct device_node *np,
>  				       const char *propname,
>  				       u32 *out_value)
>