linux-kernel - Re: [PATCH] of: Add device_type access helper functions

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Date:   Tue, 4 Sep 2018 20:55:48 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of: Add device_type access helper functions

On 08/30/18 11:52, Rob Herring wrote:
> In preparation to remove direct access to device_node.type, add
> of_node_is_type() and of_node_get_device_type() helpers to check and
> retrieve the device type.
> 
> Cc: Frank Rowand <frowand.list@...il.com>
> Signed-off-by: Rob Herring <robh@...nel.org>
> ---
>  include/linux/of.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/linux/of.h b/include/linux/of.h
> index a40f63a36afa..506beca9588d 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -980,6 +980,18 @@ static inline struct device_node *of_find_matching_node(
>  	return of_find_matching_node_and_match(from, matches, NULL);
>  }
>  
> +static inline const char *of_node_get_device_type(const struct device_node *np)
> +{
> +	return of_get_property(np, "type", NULL);

I'm a little confused.  The patch comment says "remove direct access to device_node.type.
device_node.type is set to the value of the property "device_type" in populate_node(),
but of_node_get_device_type() is looking for property "type".


> +}> +
> +static inline bool of_node_is_type(const struct device_node *np, const char *type)
> +{
> +	const char *match = of_node_get_device_type(np);
> +
> +	return np && match && type && !of_prop_cmp(match, type);
> +}
> +
>  /**
>   * of_property_count_u8_elems - Count the number of u8 elements in a property
>   *
> 

I'd like to see one or two examples of how you plan to use of_node_get_device_type()
(outside of of_node_is_type()) and examples of planned use of of_node_is_type() so
I can better understand anticipated usage.  Complete, clean patches not needed for
the examples, just enough text for me to see the resulting code change where the
helpers are used.

-Frank