linux-kernel - Re: [PATCH v1 2/6] device property: Add fwnode_property_match_property

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Date:   Wed, 9 Aug 2023 18:59:44 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Antoniu Miclaus <antoniu.miclaus@...log.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Gerald Loacker <gerald.loacker@...fvision.net>,
        Gwendal Grignou <gwendal@...omium.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-iio@...r.kernel.org, Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>
Subject: Re: [PATCH v1 2/6] device property: Add
 fwnode_property_match_property_string()

On Tue,  8 Aug 2023 19:27:56 +0300
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> Sometimes the users want to match the single value string property
> against an array of predefined strings. Create a helper for them.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/base/property.c  | 35 +++++++++++++++++++++++++++++++++++
>  include/linux/property.h | 12 ++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index 3bb9505f1631..8f8e2a6816bc 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -498,6 +498,41 @@ int fwnode_property_match_string(const struct fwnode_handle *fwnode,
>  }
>  EXPORT_SYMBOL_GPL(fwnode_property_match_string);
>  
> +/**
> + * fwnode_property_match_property_string - find a property string value in an array and return index
> + * @fwnode: Firmware node to get the property of
> + * @propname: Name of the property holding the string value
> + * @array: String array to search in
> + * @n: Size of the @array
> + *
> + * Find a property string value in a given @array and if it is found return
> + * the index back.
> + *
> + * Return: index, starting from %0, if the string value was found in the @array (success),
> + *	   %-ENOENT when the string value was not found in the @array,
> + *	   %-EINVAL if given arguments are not valid,
> + *	   %-ENODATA if the property does not have a value,
> + *	   %-EPROTO or %-EILSEQ if the property is not a string,
> + *	   %-ENXIO if no suitable firmware interface is present.
> + */
> +int fwnode_property_match_property_string(const struct fwnode_handle *fwnode,
> +	const char *propname, const char * const *array, size_t n)

Hi Andy,

Whilst I'm not 100% sold on adding ever increasing complexity to what we
match, this one feels like a common enough thing to be worth providing.

Looking at the usecases I wonder if it would be better to pass in
an unsigned int *ret which is only updated on a match?

That way the common properties approach of not checking the return value
if we have an optional property would apply.

e.g. patch 3 would end up with a block that looks like:

	st->input_mode = ADMV1014_IQ_MODE;
	device_property_match_property_string(&spi->dev, "adi,input-mode",
					      input_mode_names,
					      ARRAY_SIZE(input_mode_names),
					      &st->input_mode);

Only neat and tidy if the thing being optionally read into is an unsigned int
though (otherwise you still need a local variable)

Jonathan


> +{
> +	const char *string;
> +	int ret;
> +
> +	ret = fwnode_property_read_string(fwnode, propname, &string);
> +	if (ret)
> +		return ret;
> +
> +	ret = match_string(array, n, string);
> +	if (ret < 0)
> +		ret = -ENOENT;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(fwnode_property_match_property_string);
> +
>  /**
>   * fwnode_property_get_reference_args() - Find a reference with arguments
>   * @fwnode:	Firmware node where to look for the reference
> diff --git a/include/linux/property.h b/include/linux/property.h
> index 8c3c6685a2ae..11f3ad6814f2 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -97,6 +97,18 @@ static inline bool device_is_compatible(const struct device *dev, const char *co
>  	return fwnode_device_is_compatible(dev_fwnode(dev), compat);
>  }
>  
> +int fwnode_property_match_property_string(const struct fwnode_handle *fwnode,
> +					  const char *propname,
> +					  const char * const *array, size_t n);
> +
> +static inline
> +int device_property_match_property_string(const struct device *dev,
> +					  const char *propname,
> +					  const char * const *array, size_t n)
> +{
> +	return fwnode_property_match_property_string(dev_fwnode(dev), propname, array, n);
> +}
> +
>  int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
>  				       const char *prop, const char *nargs_prop,
>  				       unsigned int nargs, unsigned int index,