linux-kernel - Re: [PATCH v5 2/4] ALSA: usb-audio: improve module param quirk

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Message-ID: <873488b5uo.wl-tiwai@suse.de>
Date: Sat, 27 Sep 2025 11:30:07 +0200
From: Takashi Iwai <tiwai@...e.de>
To: cryolitia@...ontech.com
Cc: Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>,
	Jonathan Corbet <corbet@....net>,
	Mingcong Bai <jeffbai@...c.io>,
	Kexy Biscuit <kexybiscuit@...c.io>,
	Nie Cheng <niecheng1@...ontech.com>,
	Zhan Jun <zhanjun@...ontech.com>,
	Feng Yuan <fengyuan@...ontech.com>,
	qaqland <anguoli@...ontech.com>,
	kernel@...ontech.com,
	linux-sound@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH v5 2/4] ALSA: usb-audio: improve module param quirk_flags

On Thu, 25 Sep 2025 11:25:17 +0200,
Cryolitia PukNgae via B4 Relay wrote:
> +static void snd_usb_init_quirk_flags(int idx, struct snd_usb_audio *chip)
> +{
> +	/* add or correct quirk bits from options */
> +	for (i = 0; i < ARRAY_SIZE(quirk_flags); i++) {
> +		if (!quirk_flags[i] || !*quirk_flags[i])
> +			break;
> +
> +		val = kstrdup(quirk_flags[i], GFP_KERNEL);
> +
> +		if (!val)
> +			return;
> +
> +		snd_usb_init_quirk_flags_parse_string(chip, val);
> +
> +		kfree(val);

For a temporary string allocation, nowadays it's better to use
__free(kfree):

	for (i = 0; i < ARRAY_SIZE(quirk_flags); i++) {
		if (!quirk_flags[i] || !*quirk_flags[i])
			break;

		char *val __free(kfree) = 
			kstrdup(quirk_flags[i], GFP_KERNEL);
		if (!val)
			return;

		snd_usb_init_quirk_flags_parse_string(chip, val);
	}

Or maybe it's even safer to pass the original string (with const) and
do kstrdup() in the callee side.  You can use __free(kfree) in the
same way in snd_usb_init_quirk_flags_parse_string().


thanks,

Takashi