Re: [PATCH v4 3/5] ALSA: usb-audio: improve module param quirk_flags

[Takashi Iwai <tiwai@suse.de>]

On Thu, 18 Sep 2025 11:24:32 +0200,
Cryolitia PukNgae via B4 Relay wrote:
> 
> From: Cryolitia PukNgae <cryolitia@uniontech.com>
> 
> For apply and unapply quirk flags more flexibly though param
> 
> Co-developed-by: Takashi Iwai <tiwai@suse.de>
> Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
> ---
>  sound/usb/card.c     |   9 ++--
>  sound/usb/quirks.c   | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>  sound/usb/quirks.h   |   3 +-
>  sound/usb/usbaudio.h |   3 ++
>  4 files changed, 126 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 0265206a8e8cf31133e8463c98fe0497d8ace89e..5837677effa1787ef9d7d02714c3ae43b1a8bc79 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -73,8 +73,8 @@ static bool lowlatency = true;
>  static char *quirk_alias[SNDRV_CARDS];
>  static char *delayed_register[SNDRV_CARDS];
>  static bool implicit_fb[SNDRV_CARDS];
> -static unsigned int quirk_flags[SNDRV_CARDS];
>  
> +char *quirk_flags[SNDRV_CARDS];

My preference is to keep this static, but pass the string value to a
function.  That is, define snd_usb_init_quirk_flags() in main.c:

static void snd_usb_init_quirk_flags(struct snd_usb_audio *chip, int indx)
{
	/* old style option found: the position-based integer value */
	if (quirk_flags[idx] &&
	    !kstrtou32(quirk_flags[idx], 0, &chip->quirk_flags)) {
		usb_audio_dbg(chip,
			      "Set quirk flags 0x%x from param based on position %d for device %04x:%04x\n",
			      chip->quirk_flags, idx,
			      USB_ID_VENDOR(chip->usb_id),
			      USB_ID_PRODUCT(chip->usb_id));
		return;
	}

	/* take the default quirk from the quirk table */
	snd_usb_init_quirk_flags_table(chip);

	/* add or correct quirk bits from options */
	for (i = 0; i < ARRAY_SIZE(quirk_flags); i++) {
		char *val __free(kfree) = NULL;

		if (!quirk_flags[i] || !*quirk_flags[i])
			continue;
		
		val = kstrdup(quirk_flags[i], GFP_KERNEL);
		if (!val)
			return;

		snd_usb_parse_quirk_string(chip, val);
	}
}
	
static int snd_usb_audio_create(....)
{
	....
	snd_usb_init_quirk_flags(chip, idx);
	....
}

The function snd_usb_parse_quirk_string() is defined in quirks.c,

void snd_usb_parse_quirk_string(struct snd_usb_audio *chip, char *val)
{
	for (p = val; p && *p;) {
		/* Each entry consists of VID:PID:flags */
		field = strsep(&p, ":");
		if (!field)
			break;
		.....
	}
}


thanks,

Takashi