Re: [PATCH v5 05/10] gpiolib: Add gpio_property_name_length()

Andy Shevchenko
2024-08-22T14:37:05Z

On Thu, Aug 22, 2024 at 05:19:58PM +0800, Chen-Yu Tsai wrote:
> The I2C device tree component prober needs to get and toggle GPIO lines
> for the components it intends to probe. These components may not use the
> same name for their GPIO lines, so the prober must go through the device
> tree, check each property to see it is a GPIO property, and get the GPIO
> line.
>
> Instead of duplicating the GPIO suffixes, or exporting them to the
> prober to do pattern matching, simply add and export a new function that
> does the pattern matching and returns the length of the GPIO name. The
> caller can then use that to copy out the name if it needs to.

...

> +/**
> + * gpio_property_name_length - Returns the GPIO name length from a property name
> + * @str: string to check

It's property name, so, I would name this 'propname'.

> + * This function checks if the given name matches the GPIO property patterns, and
> + * returns the length of the name of the GPIO. The pattern is "*-<GPIO suffix>"
> + * or just "<GPIO suffix>".
> + *
> + * Returns:
> + * The length of the string before '-' if it matches "*-<GPIO suffix>", or

What about "x-y-gpios"? It's unclear what will be the behaviour.

> + * 0 if no name part, just the suffix, or
> + * -EINVAL if the string doesn't match the pattern.
> + */
> +int gpio_property_name_length(const char *str)

gpio_get_... ?

> +{
> + size_t len;
> +
> + len = strlen(str);

If it has a thousands characters...?

> + /* string need to be at minimum len(gpio) */
> + if (len < 4)
> + return -EINVAL;

Do we really need it here? See below as well.

> + /* Check for no-name case: "gpio" / "gpios" */
> + for (const char *const *p = gpio_suffixes; *p; p++)
> + if (!strcmp(str, *p))
> + return 0;

> + for (size_t i = len - 4; i > 0; i--) {
> + /* find right-most '-' and check if remainder matches suffix */
> + if (str[i] != '-')
> + continue;
> +
> + for (const char *const *p = gpio_suffixes; *p; p++)
> + if (!strcmp(str + i + 1, *p))
> + return i;
> +
> + return -EINVAL;
> + }

This can be combined with the above

for (const char *const *p = gpio_suffixes; *p; p++) {
/*
* Find right-most '-' and check if remainder matches suffix.
* If no separator found, check for no-name cases.
*/
dash = strrchr(propname, '-');
if (!strcmp(dash ? dash + 1 : propname, *p))
return i;
}

> + return -EINVAL;
> +}

--
With Best Regards,
Andy Shevchenko