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

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Date:   Wed, 5 Sep 2018 08:17:03 -0500
From:   Rob Herring <robh@...nel.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: Add device_type access helper functions

On Tue, Sep 4, 2018 at 10:55 PM Frank Rowand <frowand.list@...il.com> wrote:
>
> 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".

Crap. That should be device_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.

See my dt/testing branch. Most cases are of_node_is_type which
replaces strcmp's of node->type. I'll be sending out the patches soon.

Rob