RE: [RFC PATCH v3 1/5] dt: add of_get_child_count helper function

[Dong Aisheng-B29396 <B29396@freescale.com>]

> -----Original Message-----
> From: Marek Vasut [mailto:marek.vasut@gmail.com]
> Sent: Wednesday, December 21, 2011 3:47 AM
> To: linux-arm-kernel@lists.infradead.org
> Cc: Dong Aisheng-B29396; linux-kernel@vger.kernel.org;
> linus.walleij@stericsson.com; s.hauer@pengutronix.de; w.sang@pengutronix.de;
> rob.herring@calxeda.com; grant.likely@secretlab.ca; kernel@pengutronix.de;
> cjb@laptop.org; devicetree-discuss@lists.ozlabs.org; Guo Shawn-R65073
> Subject: Re: [RFC PATCH v3 1/5] dt: add of_get_child_count helper function
> Importance: High
> 
> > From: Dong Aisheng <dong.aisheng@linaro.org>
> >
> > Currently most code to get child count in kernel are almost same, add
> > a helper to implement this function for dt to use.
> >
> > ---
> > Changes v1->v2:
> >  * change the name from of_get_child_number to of_get_child_count
> >
> > Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
> > Cc: Grant Likely <grant.likely@secretlab.ca>
> > Cc: Rob Herring <rob.herring@calxeda.com>
> > ---
> >  include/linux/of.h |   16 ++++++++++++++++
> >  1 files changed, 16 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/of.h b/include/linux/of.h index
> > 4948552..d0d91a1 100644
> > --- a/include/linux/of.h
> > +++ b/include/linux/of.h
> > @@ -189,6 +189,17 @@ extern struct device_node
> > *of_get_next_child(const struct device_node *node, for (child =
> > of_get_next_child(parent, NULL); child != NULL; \
> >  	     child = of_get_next_child(parent, child))
> >
> > +static inline int of_get_child_count(const struct device_node *np) {
> > +	struct device_node *child = NULL;
> > +	int num = 0;
> > +
> > +	while ((child = of_get_next_child(np, child)))
> 
> The assignment in this condition really looks eerie, maybe just rewrite it to do
> { } while () ? Also, aren't the parenthesis unnecessary?
> 
Yes, one more parenthesis. I will remove it. Thanks.
For the condition, it's a little trick but I guess for a helper function
it's ok right? And there're already many places using like this.

Regards
Dong Aisheng

> M
> > +		num++;
> > +
> > +	return num;
> > +}
> > +
> >  extern struct device_node *of_find_node_with_property(
> >  	struct device_node *from, const char *prop_name);
> >  #define for_each_node_with_property(dn, prop_name) \
> > @@ -262,6 +273,11 @@ static inline bool of_have_populated_dt(void)
> >  #define for_each_child_of_node(parent, child) \
> >  	while (0)
> >
> > +static inline int of_get_child_count(const struct device_node *np)
> > +{
> > +	return -ENOSYS;
> > +}
> > +
> >  static inline int of_device_is_compatible(const struct device_node
> > *device, const char *name)
> >  {