Re: [PATCH 01/99] lib: Add option iterator

[Thomas Zimmermann]

Hi

Am 06.03.23 um 23:37 schrieb Randy Dunlap:
[...]
> > + *
> > + * The call to option_iter_init() initializes the iterator instance
> > + * from the option string. The while loop walks over the individual
> > + * options in the sting and returns each in the second argument. The
> > + * returned memory is owned by the iterator instance and callers may
> > + * not modify or free it. The call to option_iter_release() frees all
> > + * resources of the iterator. This process does not modify the original
> > + * option string. If the option string contains an empty option (i.e.,
> > + * two commas next to each other), option_iter_next() skips the empty
> > + * option automatically.
>
> Is that latter skipping over a ",," automatically something that you have
> observed as needed?

It's not strictly needed for correctness, but many of those fbdev 
drivers contain code to do that. Like this one:


https://elixir.bootlin.com/linux/v6.2/source/drivers/video/fbdev/vesafb.c#L217

So doing it in the _incr() helper seems useful

> I can imagine a driver or module wanting to know that an empty string
> was entered (i.e., ",,").

I only looked at fbdev drivers, but none of them cared about empty 
strings. They all have named options and/or key-value pairs.

> > + */
> > +
> > +/**
> > + * option_iter_init - Initializes an option iterator
> > + * @iter:	the iterator to initialize
> > + * @options:	the options string
> > + */
> > +void option_iter_init(struct option_iter *iter, const char *options)
> > +{
> > +	if (options && *options)
> > +		iter->optbuf = kstrdup(options, GFP_KERNEL); // can be NULL
> > +	else
> > +		iter->optbuf = NULL;
> > +	iter->next_opt = iter->optbuf;
> > +}
> > +EXPORT_SYMBOL(option_iter_init);
> > +
> > +/**
> > + * option_iter_release - Releases an option iterator's resources
> > + * @iter:	the iterator
> > + */
> > +void option_iter_release(struct option_iter *iter)
> > +{
> > +	kfree(iter->optbuf);
> > +	iter->next_opt = NULL;
> > +}
> > +EXPORT_SYMBOL(option_iter_release);
> > +
> > +/**
> > + * option_iter_incr - Return current option and advance to the next
> > + * @iter:	the iterator
> > + *
> > + * Returns:
>
>   * Return:
> matches kernel-doc notation documentation.
>
> > + * The current option string, or NULL if there are no more options.
> > + */
> > +const char *option_iter_incr(struct option_iter *iter)
> > +{
> > +	char *opt;
> > +
> > +	if (!iter->next_opt) { // can be OK if kstrdup failed
> > +		if (iter->optbuf) // iter has already been released; logic error
> > +			pr_err("Incrementing option iterator without string\n");
> > +		return NULL;
> > +	}
> > +
> > +	do {
> > +		opt = strsep(&iter->next_opt, ",");
> > +		if (!opt)
> > +			return NULL;
> > +	} while (!*opt); // found empty option string, try next
> > +
> > +	return opt;
> > +}
> > +EXPORT_SYMBOL(option_iter_incr);
>
> Looks useful. Thanks.

Thanks.

Best regards
Thomas

>

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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