Re: [PATCH] of: Create function for counting number of phandles in a property

From: Grant Likely
Date: Tue Feb 12 2013 - 13:20:32 EST

On Mon, 11 Feb 2013 12:26:15 +0100, Andreas Larsson <andreas@xxxxxxxxxxx> wrote:
> On 2013-02-11 00:58, Grant Likely wrote:
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index 2390ddb..e1120a2 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -1025,12 +1025,13 @@ EXPORT_SYMBOL(of_parse_phandle);
> > * To get a device_node of the `node2' node you may call this:
> > * of_parse_phandle_with_args(node3, "list", "#list-cells", 1, &args);
> > */
> > -int of_parse_phandle_with_args(const struct device_node *np, const char *list_name,
> > - const char *cells_name, int index,
> > - struct of_phandle_args *out_args)
> > +static int __of_parse_phandle_with_args(const struct device_node *np,
> > + const char *list_name,
> > + const char *cells_name, int index,
> > + struct of_phandle_args *out_args)
> > {
> > const __be32 *list, *list_end;
> > - int size, cur_index = 0;
> > + int rc = 0, size, cur_index = 0;
> > uint32_t count = 0;
> > struct device_node *node = NULL;
> > phandle phandle;
> > @@ -1059,12 +1060,14 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
> > if (!node) {
> > pr_err("%s: could not find phandle\n",
> > np->full_name);
> > + rc = -EINVAL;
> > break;
> > }
> > if (of_property_read_u32(node, cells_name, &count)) {
> > pr_err("%s: could not get %s for %s\n",
> > np->full_name, cells_name,
> > node->full_name);
> > + rc = -EINVAL;
> > break;
> > }
> >
> > @@ -1075,6 +1078,7 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
> > if (list + count > list_end) {
> > pr_err("%s: arguments longer than property\n",
> > np->full_name);
> > + rc = -EINVAL;
> > break;
> > }
> > }
> > @@ -1086,8 +1090,10 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
> > * or return -ENOENT for an empty entry.
> > */
> > if (cur_index == index) {
> > - if (!phandle)
> > - return -ENOENT;
> > + if (!phandle) {
> > + rc = -ENOENT;
> > + break;
> > + }
> >
> > if (out_args) {
> > int i;
> > @@ -1098,22 +1104,54 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
> > for (i = 0; i < count; i++)
> > out_args->args[i] = be32_to_cpup(list++);
> > }
> > - return 0;
> > +
> > + rc = 0;
> > + break;
> > }
> >
> > of_node_put(node);
> > node = NULL;
> > list += count;
> > cur_index++;
> > + rc = cur_index;
> > }
> >
> > /* Loop exited without finding a valid entry; return an error */
> > if (node)
> > of_node_put(node);
> > - return -EINVAL;
> > + return rc;
> > +}
> > +
> > +int of_parse_phandle_with_args(const struct device_node *np, const char *list_name,
> > + const char *cells_name, int index,
> > + struct of_phandle_args *out_args)
> > +{
> > + return __of_parse_phandle_with_args(np, list_name, cells_name, index, out_args);
> > }
> > EXPORT_SYMBOL(of_parse_phandle_with_args);
>
> Will this not result in a situation where a call to
> of_parse_phandle_with_args with an out of bounds index returns the
> number of tuples instead of an error code and possibly some caller that
> uses the this count as a phandle instead of handling an error?

Yes, you are right about the out of bounds index. I had meant to write
the following in __of_parse_phandle_with_args:

return (index < 0) ? rc : -ENOENT;

Which should solve that problem.

>
> Of course of_count_phandle_with_args can be used to make sure that no
> such call is made in the first place, but that is another story.

Not really, the __ function still has to test for a negative index.
However, it can at least make sure the index passed is not negative so
you can't get count behaviour when calling for a parse. How about:

int of_parse_phandle_with_args(const struct device_node *np, const char *list_name,
const char *cells_name, int index,
struct of_phandle_args *out_args)
{
if (index < 0)
return -EINVAL;
return __of_parse_phandle_with_args(np, list_name, cells_name, index, out_args);
}


>
> Related to this is that Case 7 in of_selftest_parse_phandle_with_args
> never gets exercised as far as I can see.

You're right. Also a bug. Fixed now.

>
>
> > diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
> > index c454f57..bdbe0f3 100644
> > --- a/include/linux/of_gpio.h
> > +++ b/include/linux/of_gpio.h
> > @@ -50,8 +50,28 @@ static inline struct of_mm_gpio_chip *to_of_mm_gpio_chip(struct gpio_chip *gc)
> > extern int of_get_named_gpio_flags(struct device_node *np,
> > const char *list_name, int index, enum of_gpio_flags *flags);
> >
> > -extern unsigned int of_gpio_named_count(struct device_node *np,
> > - const char* propname);
> > +/**
> > + * of_gpio_named_count - Count GPIOs for a device
> > + * @np: device node to count GPIOs for
> > + * @propname: property name containing gpio specifier(s)
> > + *
> > + * The function returns the count of GPIOs specified for a node.
> > + *
> > + * Note that the empty GPIO specifiers counts too. For example,
> > + *
> > + * gpios = <0
> > + * &pio1 1 2
> > + * 0
> > + * &pio2 3 4>;
> > + *
> > + * defines four GPIOs (so this function will return 4), two of which
> > + * are not specified. Returns -EINVAL for an incorrectly formed gpios
> > + * property.
> > + */
> > +static int of_gpio_named_count(struct device_node *np, const char* propname)
> > +{
> > + return of_count_phandle_with_args(np, propname, "#gpio-cells");
> > +}
>
> Should this be static inline int?

Yes.

>
> I think it would be good to also document that it also returns -ENOENT
> when the propname property is missing, which might be an important case
> to distinguish from the -EINVAL case.

Done. I'll post a new version shortly.

g.

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