linux-kernel - Re: [PATCH 1/2] lib/string_helpers: Introduce strsplit

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Date:   Fri, 8 Jul 2022 14:13:14 +0200
From:   Cezary Rojewski <cezary.rojewski@...el.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Andy Shevchenko <andy@...nel.org>, Mark Brown <broonie@...nel.org>,
        "ALSA Development Mailing List" <alsa-devel@...a-project.org>,
        Takashi Iwai <tiwai@...e.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        <amadeuszx.slawinski@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Péter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        "Ranjani Sridharan" <ranjani.sridharan@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        "Kai Vehmanen" <kai.vehmanen@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>
Subject: Re: [PATCH 1/2] lib/string_helpers: Introduce strsplit_u32()

On 2022-07-08 1:46 PM, Andy Shevchenko wrote:
> On Fri, Jul 8, 2022 at 1:33 PM Cezary Rojewski
> <cezary.rojewski@...el.com> wrote:

...

>> When I'd written the very first version of this function many months
>> ago, get_options() looked as it does not fulfill our needs. It seems to
>> be true even today: caller needs to know the number of elements in an
>> array upfront.
> 
> Have you read a kernel doc for it? It does return the number of
> elements at the first pass.

Yes, I've checked several parts of it. Perhaps I did miss something but 
simple_strtoull() doc reads: use kstrtox() instead. Thus the 
strsplit_u32() makes use of kstrtox().

>> Also, kstrtox() takes into account '0x' and modifies the
>> base accordingly if that's the case. simple_strtoull() looks as not
>> capable of doing the same thing.
> 
> How come?! It does parse all known prefixes: 0x, 0, +, -.

Hmm.. doc says that it stops at the first non-digit character. Will 
re-check.

>> The goal is to be able to parse input such as:
>>
>> 0x1000003,0,0,0x1000004,0,0
>>
>> into a sequence of 6 uints, filling the *tkns and *num_tkns for the caller.
> 
> Yes. Have you checked the test cases for get_options()?
> 

...

>> avs-driver, which is also part of the ASoC framework has very similar
>> debug-interface. I believe there's no need to duplicate the functions -
>> move them to common code instead.
> 
> Taking the above into account, please try to use get_options() and
> then tell me what's not working with it. If so, we will add test cases
> to get_options() and fix it.

There is a difference:

	// get_options
	int ints[5];

	s = get_options(str, ARRAY_SIZE(ints), ints);

	// strsplit_u32()
	u32 *tkns, num_tkns;

	ret = strsplit_u32(str, delim, &tkns, &num_tkns);

Nothing has been told upfront for in the second case.