linux-kernel - Re: [PATCH 1/2] ASoC: Intel: maxim-common: get codec number from ACPI

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Date:   Mon, 24 Jul 2023 12:52:14 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Brent Lu <brent.lu@...el.com>, alsa-devel@...a-project.org,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, linux-kernel@...r.kernel.org,
        Yong Zhi <yong.zhi@...el.com>,
        Ajye Huang <ajye_huang@...pal.corp-partner.google.com>,
        Uday M Bhat <uday.m.bhat@...el.com>,
        Terry Cheong <htcheong@...omium.org>,
        Mac Chiang <mac.chiang@...el.com>,
        "Dharageswari . R" <dharageswari.r@...el.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Subject: Re: [PATCH 1/2] ASoC: Intel: maxim-common: get codec number from ACPI

On Mon, Jul 24, 2023 at 11:08:17AM +0200, Pierre-Louis Bossart wrote:
> On 7/20/23 11:26, Brent Lu wrote:

...

> > +/* helper function to get the number of specific codec */

...and leak a lot of reference counts...

> > +static int get_num_codecs(const char *hid)
> > +{
> > +	struct acpi_device *adev = NULL;
> > +	int dev_num = 0;
> > +
> > +	do {
> > +		adev = acpi_dev_get_next_match_dev(adev, hid, NULL, -1);
> 
> Humm, I am a bit worried about reference counts.
> 
> See
> https://elixir.bootlin.com/linux/latest/source/drivers/acpi/utils.c#L916,
> it's not clear to me where the get() is done.
> 
> Adding Andy to make sure this is done right.

Thank you for Cc'ing.

Yes, the above code is problematic. One has to use the respective for_each
macro (defined nearby the used API).

> > +		if (adev)
> > +			dev_num++;
> > +	} while (adev != NULL);
> > +
> > +	return dev_num;
> > +}

-- 
With Best Regards,
Andy Shevchenko