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

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Date:   Fri, 8 Jul 2022 13:46:56 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Cezary Rojewski <cezary.rojewski@...el.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 Fri, Jul 8, 2022 at 1:33 PM Cezary Rojewski
<cezary.rojewski@...el.com> wrote:
> On 2022-07-08 12:22 PM, Andy Shevchenko wrote:
> > On Thu, Jul 7, 2022 at 11:03 AM Cezary Rojewski
> > <cezary.rojewski@...el.com> wrote:
> >>
> >> Add strsplit_u32() and its __user variant to allow for splitting
> >> specified string into array of u32 tokens.
> >
> > And I believe we have more of this done in old code.
> > Since all callers use ',' as a delimiter, have you considered using
> > get_options()?
>
>
> Thanks for your input, Andy.
>
> 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.

> 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, +, -.

> 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()?

> >> Originally this functionality was added for the SOF sound driver. As
> >> more users are on the horizon, relocate it so it becomes a common good.
> >
> > Maybe it can be fixed just there.
>
> 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.

-- 
With Best Regards,
Andy Shevchenko