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

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.

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


> 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?

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.


Cheers,
Andreas Larsson



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