[PATCH v3 0/4] ALSA: usb-audio: add module param device_quirk_flags

[PATCH v3 0/4] ALSA: usb-audio: add module param device_quirk_flags

[Cryolitia PukNgae via B4 Relay]

As an implementation of what has been discussed previously[1].

1. https://lore.kernel.org/all/87h5xm5g7f.wl-tiwai@suse.de/

Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
---
Changes in v3:
- Instead of a new param, improve the existed one.
- Link to v2: https://lore.kernel.org/r/20250912-sound-v2-0-01ea3d279f4b@uniontech.com

Changes in v2:
- Cleaned up some internal rebase confusion, sorry for that
- Link to v1: https://lore.kernel.org/r/20250912-sound-v1-0-cc9cfd9f2d01@uniontech.com

---
Cryolitia PukNgae (4):
      ALSA: usb-audio: add two-way convert between name and bit for QUIRK_FLAG_*
      param: export param_array related functions
      ALSA: usb-audio: add module param device_quirk_flags
      ALSA: doc: add docs about device_device_quirk_flags in snd-usb-audio

 Documentation/sound/alsa-configuration.rst | 112 ++++++++++++------
 include/linux/moduleparam.h                |   3 +
 kernel/params.c                            |   9 +-
 sound/usb/card.c                           | 177 +++++++++++++++++++++++++++--
 sound/usb/quirks.c                         | 123 +++++++++++++++++++-
 sound/usb/quirks.h                         |   5 +
 sound/usb/usbaudio.h                       |  15 +++
 7 files changed, 394 insertions(+), 50 deletions(-)
---
base-commit: 4c421c40c8b30ab7aae1edc7f7e294fcd33fc186
change-id: 20250910-sound-a91c86c92dba

Best regards,
-- 
Cryolitia PukNgae <cryolitia@uniontech.com>

[PATCH v3 1/4] ALSA: usb-audio: add two-way convert between name and bit for QUIRK_FLAG_*

[Cryolitia PukNgae via B4 Relay]

From: Cryolitia PukNgae <cryolitia@uniontech.com>

Also improve debug logs for applied quirks

Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
---
 sound/usb/quirks.c   | 82 +++++++++++++++++++++++++++++++++++++++++++++++++---
 sound/usb/quirks.h   |  3 ++
 sound/usb/usbaudio.h |  1 +
 3 files changed, 82 insertions(+), 4 deletions(-)

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index d736a4750356597bfb0f9d5ab01cdaeaac0f907c..94854f352b1702b491e1bf3c8b769f7088e03976 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -2446,6 +2446,62 @@ static const struct usb_audio_quirk_flags_table quirk_flags_table[] = {
 	{} /* terminator */
 };
 
+static const char *const snd_usb_audio_quirk_flag_names[] = {
+	"get_sample_rate",
+	"share_media_device",
+	"align_transfer",
+	"tx_length",
+	"playback_first",
+	"skip_clock_selector",
+	"ignore_clock_source",
+	"itf_usb_dsd_dac",
+	"ctl_msg_delay",
+	"ctl_msg_delay_1m",
+	"ctl_msg_delay_5m",
+	"iface_delay",
+	"validate_rates",
+	"disable_autosuspend",
+	"ignore_ctl_error",
+	"dsd_raw",
+	"set_iface_first",
+	"generic_implicit_fb",
+	"skip_implicit_fb",
+	"iface_skip_close",
+	"force_iface_reset",
+	"fixed_rate",
+	"mic_res_16",
+	"mic_res_384",
+	"mixer_playback_min_mute",
+	"mixer_capture_min_mute",
+	NULL
+};
+
+const char *snd_usb_quirk_flag_find_name(unsigned long index)
+{
+	if (index >= ARRAY_SIZE(snd_usb_audio_quirk_flag_names))
+		return NULL;
+
+	return snd_usb_audio_quirk_flag_names[index];
+}
+
+u32 snd_usb_quirk_flags_from_name(char *name)
+{
+	u32 flag = 0;
+	u32 i;
+
+	if (!name || !*name)
+		return 0;
+
+	for (i = 0; snd_usb_audio_quirk_flag_names[i]; i++) {
+		if (strcmp(name, snd_usb_audio_quirk_flag_names[i]) == 0) {
+			flag = (1U << i);
+			break;
+		}
+	}
+
+	return flag;
+}
+
 void snd_usb_init_quirk_flags(struct snd_usb_audio *chip)
 {
 	const struct usb_audio_quirk_flags_table *p;
@@ -2454,10 +2510,28 @@ void snd_usb_init_quirk_flags(struct snd_usb_audio *chip)
 		if (chip->usb_id == p->id ||
 		    (!USB_ID_PRODUCT(p->id) &&
 		     USB_ID_VENDOR(chip->usb_id) == USB_ID_VENDOR(p->id))) {
-			usb_audio_dbg(chip,
-				      "Set quirk_flags 0x%x for device %04x:%04x\n",
-				      p->flags, USB_ID_VENDOR(chip->usb_id),
-				      USB_ID_PRODUCT(chip->usb_id));
+			unsigned long flags = p->flags;
+			unsigned long bit;
+
+			for_each_set_bit(bit, &flags,
+					 BYTES_TO_BITS(sizeof(p->flags))) {
+				const char *name =
+					snd_usb_audio_quirk_flag_names[bit];
+
+				if (name)
+					usb_audio_dbg(chip,
+						      "Set quirk flag %s for device %04x:%04x\n",
+						      name,
+						      USB_ID_VENDOR(chip->usb_id),
+						      USB_ID_PRODUCT(chip->usb_id));
+				else
+					usb_audio_warn(chip,
+						       "Set unknown quirk flag 0x%lx for device %04x:%04x\n",
+						       bit,
+						       USB_ID_VENDOR(chip->usb_id),
+						       USB_ID_PRODUCT(chip->usb_id));
+			}
+
 			chip->quirk_flags |= p->flags;
 			return;
 		}
diff --git a/sound/usb/quirks.h b/sound/usb/quirks.h
index f9bfd5ac7bab01717de3a76227482a128bf73165..bd5baf2b193a1985f3a0e52bf4a77ca741364769 100644
--- a/sound/usb/quirks.h
+++ b/sound/usb/quirks.h
@@ -50,4 +50,7 @@ void snd_usb_audioformat_attributes_quirk(struct snd_usb_audio *chip,
 
 void snd_usb_init_quirk_flags(struct snd_usb_audio *chip);
 
+const char *snd_usb_quirk_flag_find_name(unsigned long flag);
+u32 snd_usb_quirk_flags_from_name(char *name);
+
 #endif /* __USBAUDIO_QUIRKS_H */
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 30b5102e3caed01eeb86d0075c41338104c58950..0a22cb4a02344b2dcf4009c560a759f2da25ca67 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -252,5 +252,6 @@ extern bool snd_usb_skip_validation;
 #define QUIRK_FLAG_MIC_RES_384		(1U << 23)
 #define QUIRK_FLAG_MIXER_PLAYBACK_MIN_MUTE	(1U << 24)
 #define QUIRK_FLAG_MIXER_CAPTURE_MIN_MUTE	(1U << 25)
+/* Please also edit snd_usb_audio_quirk_flag_names */
 
 #endif /* __USBAUDIO_H */

-- 
2.51.0

[PATCH v3 2/4] param: export param_array related functions

[Cryolitia PukNgae via B4 Relay]

From: Cryolitia PukNgae <cryolitia@uniontech.com>

- int param_array_set(const char *val, const struct kernel_param *kp);
- int param_array_get(char *buffer, const struct kernel_param *kp);
- void param_array_free(void *arg);

It would be helpful for the new module param we designed in
snd_usb_audio, in order to run additional custom codes when params
are set in runtime, and re-use the extisted codes in param.c

Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
---
 include/linux/moduleparam.h | 3 +++
 kernel/params.c             | 9 ++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 3a25122d83e2802e6e6a1475a52816251498b26a..4ef09ad2004789855bd21783029c653fac94b9dd 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -593,6 +593,9 @@ enum hwparam_type {
 
 
 extern const struct kernel_param_ops param_array_ops;
+extern int param_array_set(const char *val, const struct kernel_param *kp);
+extern int param_array_get(char *buffer, const struct kernel_param *kp);
+extern void param_array_free(void *arg);
 
 extern const struct kernel_param_ops param_ops_string;
 extern int param_set_copystring(const char *val, const struct kernel_param *);
diff --git a/kernel/params.c b/kernel/params.c
index b96cfd693c9968012d42acb85611fee1acd47790..a936e018a1c6d0bf2b6b4566f80751840366f652 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -462,7 +462,7 @@ static int param_array(struct module *mod,
 	return 0;
 }
 
-static int param_array_set(const char *val, const struct kernel_param *kp)
+int param_array_set(const char *val, const struct kernel_param *kp)
 {
 	const struct kparam_array *arr = kp->arr;
 	unsigned int temp_num;
@@ -471,8 +471,9 @@ static int param_array_set(const char *val, const struct kernel_param *kp)
 			   arr->elemsize, arr->ops->set, kp->level,
 			   arr->num ?: &temp_num);
 }
+EXPORT_SYMBOL(param_array_set);
 
-static int param_array_get(char *buffer, const struct kernel_param *kp)
+int param_array_get(char *buffer, const struct kernel_param *kp)
 {
 	int i, off, ret;
 	const struct kparam_array *arr = kp->arr;
@@ -492,8 +493,9 @@ static int param_array_get(char *buffer, const struct kernel_param *kp)
 	buffer[off] = '\0';
 	return off;
 }
+EXPORT_SYMBOL(param_array_get);
 
-static void param_array_free(void *arg)
+void param_array_free(void *arg)
 {
 	unsigned int i;
 	const struct kparam_array *arr = arg;
@@ -502,6 +504,7 @@ static void param_array_free(void *arg)
 		for (i = 0; i < (arr->num ? *arr->num : arr->max); i++)
 			arr->ops->free(arr->elem + arr->elemsize * i);
 }
+EXPORT_SYMBOL(param_array_free);
 
 const struct kernel_param_ops param_array_ops = {
 	.set = param_array_set,

-- 
2.51.0

[PATCH v3 3/4] ALSA: usb-audio: add module param device_quirk_flags

[Cryolitia PukNgae via B4 Relay]

From: Cryolitia PukNgae <cryolitia@uniontech.com>

For apply and unapply quirk flags more flexibly though param and sysfs

Co-developed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
---
 sound/usb/card.c     | 177 ++++++++++++++++++++++++++++++++++++++++++++++++---
 sound/usb/quirks.c   |  41 ++++++++++++
 sound/usb/quirks.h   |   2 +
 sound/usb/usbaudio.h |  14 ++++
 4 files changed, 226 insertions(+), 8 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 0265206a8e8cf31133e8463c98fe0497d8ace89e..743aae910cfdf540c6677c6846061754f36a8c1b 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];
 bool snd_usb_use_vmalloc = true;
 bool snd_usb_skip_validation;
 
@@ -103,13 +103,161 @@ module_param_array(delayed_register, charp, NULL, 0444);
 MODULE_PARM_DESC(delayed_register, "Quirk for delayed registration, given by id:iface, e.g. 0123abcd:4.");
 module_param_array(implicit_fb, bool, NULL, 0444);
 MODULE_PARM_DESC(implicit_fb, "Apply generic implicit feedback sync mode.");
-module_param_array(quirk_flags, uint, NULL, 0444);
-MODULE_PARM_DESC(quirk_flags, "Driver quirk bit flags.");
 module_param_named(use_vmalloc, snd_usb_use_vmalloc, bool, 0444);
 MODULE_PARM_DESC(use_vmalloc, "Use vmalloc for PCM intermediate buffers (default: yes).");
 module_param_named(skip_validation, snd_usb_skip_validation, bool, 0444);
 MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no).");
 
+DEFINE_MUTEX(device_quirk_mutex); /* protects quirk_flags && device_quirk_list */
+LIST_HEAD(device_quirk_list);
+
+static void free_device_quirk_list(void)
+{
+	struct device_quirk_entry *pos, *tmp;
+
+	list_for_each_entry_safe(pos, tmp, &device_quirk_list, list) {
+		list_del(&pos->list);
+		kfree(pos);
+	}
+}
+
+static int device_quirks_param_set(const char *value,
+				   const struct kernel_param *kp)
+{
+	u32 mask_flags, unmask_flags, bit;
+	struct device_quirk_entry *data;
+	char *val, *p, *field, *flag;
+	bool is_unmask;
+	u16 vid, pid;
+	int err = 0;
+	size_t i;
+
+	mutex_lock(&device_quirk_mutex);
+
+	memset(quirk_flags, 0, sizeof(quirk_flags));
+
+	err = param_array_set(value, kp);
+	if (err)
+		goto unlock;
+
+	free_device_quirk_list();
+
+	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) {
+			err = -ENOMEM;
+			goto unlock;
+		}
+
+		for (p = val; p && *p;) {
+			/* Each entry consists of VID:PID:flags */
+			field = strsep(&p, ":");
+			if (!field)
+				break;
+
+			if (strcmp(field, "*") == 0)
+				vid = 0;
+			else if (kstrtou16(field, 16, &vid))
+				break;
+
+			field = strsep(&p, ":");
+			if (!field)
+				break;
+
+			if (strcmp(field, "*") == 0)
+				pid = 0;
+			else if (kstrtou16(field, 16, &pid))
+				break;
+
+			field = strsep(&p, ";");
+			if (!field || !*field)
+				break;
+
+			/* Collect the flags */
+			mask_flags = 0;
+			unmask_flags = 0;
+			while (field && *field) {
+				flag = strsep(&field, "|");
+
+				if (!flag)
+					break;
+
+				if (*flag == '!') {
+					is_unmask = true;
+					flag++;
+				} else {
+					is_unmask = false;
+				}
+
+				if (!kstrtou32(flag, 16, &bit)) {
+					if (is_unmask)
+						unmask_flags |= bit;
+					else
+						mask_flags |= bit;
+
+					break;
+				}
+
+				bit = snd_usb_quirk_flags_from_name(flag);
+
+				if (bit) {
+					if (is_unmask)
+						unmask_flags |= bit;
+					else
+						mask_flags |= bit;
+				} else {
+					pr_warn("snd_usb_audio: unknown flag %s while parsing param device_quirk_flags\n",
+						field);
+				}
+			}
+
+			data = kzalloc(sizeof(*data), GFP_KERNEL);
+
+			if (!data) {
+				kfree(val);
+				err = -ENOMEM;
+				goto unlock;
+			}
+
+			data->vid = vid;
+			data->pid = pid;
+			data->mask_flags = mask_flags;
+			data->unmask_flags = unmask_flags;
+
+			INIT_LIST_HEAD(&data->list);
+			list_add(&data->list, &device_quirk_list);
+		}
+
+		kfree(val);
+	}
+
+unlock:
+	mutex_unlock(&device_quirk_mutex);
+	return err;
+}
+
+static const struct kernel_param_ops quirk_flags_param_ops = {
+	.set = device_quirks_param_set,
+	.get = param_array_get,
+	.free = param_array_free,
+};
+
+static struct kparam_array quirk_flags_param_array = {
+	.max = SNDRV_CARDS,
+	.elemsize = sizeof(char *),
+	.num = NULL,
+	.ops = &param_ops_charp,
+	.elem = &quirk_flags,
+};
+
+device_param_cb(quirk_flags, &quirk_flags_param_ops, &quirk_flags_param_array,
+		0644);
+MODULE_PARM_DESC(quirk_flags, "Add/modify USB audio quirks");
+
 /*
  * we keep the snd_usb_audio_t instances by ourselves for merging
  * the all interfaces on the same card as one sound device.
@@ -750,10 +898,7 @@ static int snd_usb_audio_create(struct usb_interface *intf,
 	INIT_LIST_HEAD(&chip->midi_v2_list);
 	INIT_LIST_HEAD(&chip->mixer_list);
 
-	if (quirk_flags[idx])
-		chip->quirk_flags = quirk_flags[idx];
-	else
-		snd_usb_init_quirk_flags(chip);
+	snd_usb_init_dynamic_quirks(idx, chip);
 
 	card->private_free = snd_usb_audio_free;
 
@@ -1290,4 +1435,20 @@ static struct usb_driver usb_audio_driver = {
 	.supports_autosuspend = 1,
 };
 
-module_usb_driver(usb_audio_driver);
+static int __init usb_audio_init(void)
+{
+	return usb_register_driver(&usb_audio_driver, THIS_MODULE,
+				   KBUILD_MODNAME);
+}
+
+static void __exit usb_audio_exit(void)
+{
+	mutex_lock(&device_quirk_mutex);
+	free_device_quirk_list();
+	mutex_unlock(&device_quirk_mutex);
+
+	usb_deregister(&usb_audio_driver);
+}
+
+module_init(usb_audio_init);
+module_exit(usb_audio_exit);
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 94854f352b1702b491e1bf3c8b769f7088e03976..ee531ffa5ab13ac8b24c670e6529d3811f927b46 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -2537,3 +2537,44 @@ void snd_usb_init_quirk_flags(struct snd_usb_audio *chip)
 		}
 	}
 }
+
+void snd_usb_init_dynamic_quirks(int idx, struct snd_usb_audio *chip)
+{
+	u16 vid = USB_ID_VENDOR(chip->usb_id);
+	u16 pid = USB_ID_PRODUCT(chip->usb_id);
+	struct device_quirk_entry *pos;
+
+	mutex_lock(&device_quirk_mutex);
+
+	/* 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));
+
+		mutex_unlock(&device_quirk_mutex);
+		return;
+	}
+
+	/* take the default quirk from the quirk table */
+	snd_usb_init_quirk_flags(chip);
+
+	/* add or correct quirk bits from options */
+	list_for_each_entry(pos, &device_quirk_list, list) {
+		if (pos->vid == 0 || (vid == pos->vid && pos->pid == 0) ||
+		    (vid == pos->vid && pid == pos->pid)) {
+			chip->quirk_flags |= pos->mask_flags;
+			chip->quirk_flags &= ~pos->unmask_flags;
+			usb_audio_dbg(chip,
+				      "Set mask quirk flag 0x%x and unmask quirk flag 0x%x from param for device %04x:%04x\n",
+				      pos->mask_flags, pos->unmask_flags,
+				      USB_ID_VENDOR(chip->usb_id),
+				      USB_ID_PRODUCT(chip->usb_id));
+		}
+	}
+
+	mutex_unlock(&device_quirk_mutex);
+}
diff --git a/sound/usb/quirks.h b/sound/usb/quirks.h
index bd5baf2b193a1985f3a0e52bf4a77ca741364769..00c2852c4769d0790a9e2a31b92f3414767c9a98 100644
--- a/sound/usb/quirks.h
+++ b/sound/usb/quirks.h
@@ -53,4 +53,6 @@ void snd_usb_init_quirk_flags(struct snd_usb_audio *chip);
 const char *snd_usb_quirk_flag_find_name(unsigned long flag);
 u32 snd_usb_quirk_flags_from_name(char *name);
 
+void snd_usb_init_dynamic_quirks(int idx, struct snd_usb_audio *chip);
+
 #endif /* __USBAUDIO_QUIRKS_H */
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 0a22cb4a02344b2dcf4009c560a759f2da25ca67..3d09d4b7950d884a2076fa48f2180a5e7c87cb3a 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -7,6 +7,8 @@
  *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
  */
 
+ #include <sound/core.h>
+
 /* handling of USB vendor/product ID pairs as 32-bit numbers */
 #define USB_ID(vendor, product) (((unsigned int)(vendor) << 16) | (product))
 #define USB_ID_VENDOR(id) ((id) >> 16)
@@ -162,9 +164,13 @@ DEFINE_CLASS(snd_usb_lock, struct __snd_usb_lock,
 	     __snd_usb_unlock_shutdown(&(_T)), __snd_usb_lock_shutdown(chip),
 	     struct snd_usb_audio *chip)
 
+extern char *quirk_flags[SNDRV_CARDS];
 extern bool snd_usb_use_vmalloc;
 extern bool snd_usb_skip_validation;
 
+extern struct mutex device_quirk_mutex;
+extern struct list_head device_quirk_list;
+
 /*
  * Driver behavior quirk flags, stored in chip->quirk_flags
  *
@@ -254,4 +260,12 @@ extern bool snd_usb_skip_validation;
 #define QUIRK_FLAG_MIXER_CAPTURE_MIN_MUTE	(1U << 25)
 /* Please also edit snd_usb_audio_quirk_flag_names */
 
+struct device_quirk_entry {
+	struct list_head list;
+	u16 vid;
+	u16 pid;
+	u32 mask_flags;
+	u32 unmask_flags;
+};
+
 #endif /* __USBAUDIO_H */

-- 
2.51.0

Re: [PATCH v3 3/4] ALSA: usb-audio: add module param device_quirk_flags

[Takashi Iwai]

On Wed, 17 Sep 2025 14:46:42 +0200,
Cryolitia PukNgae via B4 Relay wrote:
> 
> From: Cryolitia PukNgae <cryolitia@uniontech.com>
> 
> For apply and unapply quirk flags more flexibly though param and sysfs
> 
> Co-developed-by: Takashi Iwai <tiwai@suse.de>
> Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>

I think an easier approach would be to rather parse the string value
at each time when probing a device and seeking for options.

That is, let's code without a mutex at first (for the permission
0444):

void snd_usb_init_dynamic_quirks(int idx, struct snd_usb_audio *chip)
{
	....
	/* old style option found: the position-based integer value */
	if (quirk_flags[idx] &&
	    !kstrtou32(quirk_flags[idx], 0, &chip->quirk_flags)) {
		usb_audio_dbg(....);
		return;
	}

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

	for (i = 0; i < ARRAY_SIZE(quirk_flags); i++) {
		if (quirk_flags[i] && *quirk_flags[i]) {
			err = parse_quirk_option(chip, quirk_flags[i]);
			if (err < 0)
				return;
		}
	}
}

and the parser would be something like:

static int parse_quirk_option(struct snd_usb_audio *chip, const char *str)
{
	char *val __free(kfree) = NULL;
	char *field;
	int pid, vid;

	if (!strchr(str, ':'))
		return 0;

	val = kstrdup(str, GFP_KERNEL);
	if (!val)
		return -ENOMEM;

	/* Each entry consists of VID:PID:flags */
	field = strsep(&p, ":");
	if (!field)
		return 0;
	if (strcmp(field, "*") == 0)
		vid = 0;
	else if (kstrtou16(field, 16, &vid))
		return 0; // can spew warning message, too

	field = strsep(&p, ":");
	if (!field)
		return 0;
	if (strcmp(field, "*") == 0)
		pid = 0;
	else if (kstrtou16(field, 16, &pid))
		return 0; // can spew warning message, too

	.... // evaluate the tokens, set or clear chip->quirk_flags accordingly
	return 0;
}

So you can just use the normal charp type for the parameters.

Once after this working, we may want to allow the dynamic module
parameter change.  Then make the parameter a special type just to take
the device_quirk_mutex at set callback, while the set callback simply
calls parm_set_charp() for the rest.  For get and free callbacks, we
can use param_get_charp() and param_free_charp() as is.
Finally, snd_usb_init_dynamic_quirks() takes the device_quirk_mutex,
and that's all.  No need for heavy cleanups or linked list handling.

Of course, it's a bit inefficient from the performance POV, but the
device probing is rather a very rare event, so the speed doesn't
matter at all.


thanks,

Takashi

[PATCH v3 4/4] ALSA: doc: add docs about device_device_quirk_flags in snd-usb-audio

[Cryolitia PukNgae via B4 Relay]

From: Cryolitia PukNgae <cryolitia@uniontech.com>

Just briefly described about the new option.

Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
---
 Documentation/sound/alsa-configuration.rst | 112 ++++++++++++++++++++---------
 1 file changed, 77 insertions(+), 35 deletions(-)

diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
index a2fb8ed251dd0294e7a62209ca15d5c32c6adfae..23ee37f24ff89a983b3dffe6312057cd84b8f579 100644
--- a/Documentation/sound/alsa-configuration.rst
+++ b/Documentation/sound/alsa-configuration.rst
@@ -2297,39 +2297,81 @@ skip_validation
     of the unit descriptor instead of a driver probe error, so that we
     can check its details.
 quirk_flags
-    Contains the bit flags for various device specific workarounds.
-    Applied to the corresponding card index.
-
-        * bit 0: Skip reading sample rate for devices
-        * bit 1: Create Media Controller API entries
-        * bit 2: Allow alignment on audio sub-slot at transfer
-        * bit 3: Add length specifier to transfers
-        * bit 4: Start playback stream at first in implement feedback mode
-        * bit 5: Skip clock selector setup
-        * bit 6: Ignore errors from clock source search
-        * bit 7: Indicates ITF-USB DSD based DACs
-        * bit 8: Add a delay of 20ms at each control message handling
-        * bit 9: Add a delay of 1-2ms at each control message handling
-        * bit 10: Add a delay of 5-6ms at each control message handling
-        * bit 11: Add a delay of 50ms at each interface setup
-        * bit 12: Perform sample rate validations at probe
-        * bit 13: Disable runtime PM autosuspend
-        * bit 14: Ignore errors for mixer access
-        * bit 15: Support generic DSD raw U32_BE format
-        * bit 16: Set up the interface at first like UAC1
-        * bit 17: Apply the generic implicit feedback sync mode
-        * bit 18: Don't apply implicit feedback sync mode
-        * bit 19: Don't closed interface during setting sample rate
-        * bit 20: Force an interface reset whenever stopping & restarting
-          a stream
-        * bit 21: Do not set PCM rate (frequency) when only one rate is
-          available for the given endpoint.
-        * bit 22: Set the fixed resolution 16 for Mic Capture Volume
-        * bit 23: Set the fixed resolution 384 for Mic Capture Volume
-        * bit 24: Set minimum volume control value as mute for devices
-          where the lowest playback value represents muted state instead
-          of minimum audible volume
-        * bit 25: Be similar to bit 24 but for capture streams
+    The option provides a refined and flexible control for applying quirk
+    flags.  It allows to specify the quirk flags for each device, and could
+    be modified dynamically via sysfs.
+    The old usage accepts an array of integers, each of which apply quirk
+    flags on the device in the order of probing.
+    e.g. ``quirk_flags=0x01,0x02`` applies get_sample_rate to the first
+    device, and share_media_device to the second device.
+    The new usage accepts a string in the format of
+    ``VID1:PID1:FLAGS1;VID2:PID2:FLAGS2;...``, where ``VIDx`` and ``PIDx``
+    specify the device, and ``FLAGSx`` specify the flags to be applied.
+    ``VIDx`` and ``PIDx`` are 4-digit hexadecimal numbers, and could be
+    specified as ``*`` to match any value.  ``FLAGSx`` could be a set of
+    flags given by name, separated by ``|``, or a hexadecimal number
+    representing the bit flags.  The available flag names are listed above.
+    An exclamation mark could be prefixed to a flag name to negate the flag.
+    For example, ``1234:abcd:mixer_playback_min_mute|!ignore_ctl_error;*:*:0x01;``
+    applies the ``mixer_playback_min_mute`` flag and clears the
+    ``ignore_ctl_error`` flag for the device 1234:abcd, and applies the
+    ``skip_sample_rate`` flag for all devices.
+
+        * bit 0: ``get_sample_rate``
+          Skip reading sample rate for devices
+        * bit 1: ``share_media_device``
+          Create Media Controller API entries
+        * bit 2: ``align_transfer``
+          Allow alignment on audio sub-slot at transfer
+        * bit 3: ``tx_length``
+          Add length specifier to transfers
+        * bit 4: ``playback_first``
+          Start playback stream at first in implement feedback mode
+        * bit 5: ``skip_clock_selector``
+          Skip clock selector setup
+        * bit 6: ``ignore_clock_source``
+          Ignore errors from clock source search
+        * bit 7: ``itf_usb_dsd_dac``
+          Indicates ITF-USB DSD based DACs
+        * bit 8: ``ctl_msg_delay``
+          Add a delay of 20ms at each control message handling
+        * bit 9: ``ctl_msg_delay_1m``
+          Add a delay of 1-2ms at each control message handling
+        * bit 10: ``ctl_msg_delay_5m``
+          Add a delay of 5-6ms at each control message handling
+        * bit 11: ``iface_delay``
+          Add a delay of 50ms at each interface setup
+        * bit 12: ``validate_rates``
+          Perform sample rate validations at probe
+        * bit 13: ``disable_autosuspend``
+          Disable runtime PM autosuspend
+        * bit 14: ``ignore_ctl_error``
+          Ignore errors for mixer access
+        * bit 15: ``dsd_raw``
+          Support generic DSD raw U32_BE format
+        * bit 16: ``set_iface_first``
+          Set up the interface at first like UAC1
+        * bit 17: ``generic_implicit_fb``
+          Apply the generic implicit feedback sync mode
+        * bit 18: ``skip_implicit_fb``
+          Don't apply implicit feedback sync mode
+        * bit 19: ``iface_skip_close``
+          Don't closed interface during setting sample rate
+        * bit 20: ``force_iface_reset``
+          Force an interface reset whenever stopping & restarting a stream
+        * bit 21: ``fixed_rate``
+          Do not set PCM rate (frequency) when only one rate is available
+          for the given endpoint
+        * bit 22: ``mic_res_16``
+          Set the fixed resolution 16 for Mic Capture Volume
+        * bit 23: ``mic_res_384``
+          Set the fixed resolution 384 for Mic Capture Volume
+        * bit 24: ``mixer_playback_min_mute``
+          Set minimum volume control value as mute for devices where the
+          lowest playback value represents muted state instead of minimum
+          audible volume
+        * bit 25: ``mixer_capture_min_mute``
+          Be similar to bit 24 but for capture streams
 
 This module supports multiple devices, autoprobe and hotplugging.
 
@@ -2344,8 +2386,8 @@ report it to the upstream.
 NB: ``quirk_alias`` option is provided only for testing / development.
 If you want to have a proper support, contact to upstream for
 adding the matching quirk in the driver code statically.
-Ditto for ``quirk_flags``.  If a device is known to require specific
-workarounds, please report to the upstream.
+Ditto for ``quirk_flags``.  If a device
+is known to require specific workarounds, please report to the upstream.
 
 Module snd-usb-caiaq
 --------------------

-- 
2.51.0

Re: [PATCH v3 4/4] ALSA: doc: add docs about device_device_quirk_flags in snd-usb-audio

[Dragan Simic]

Hello Cryolitia,

On 2025-09-17 14:46, Cryolitia PukNgae via B4 Relay wrote:
> From: Cryolitia PukNgae <cryolitia@uniontech.com>
> 
> Just briefly described about the new option.
> 
> Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>

Isn't the patch subject a bit wrong, and should contain
"device quirk_flags" instead of "device_device_quirk_flags"?

Re: [PATCH v3 4/4] ALSA: doc: add docs about device_device_quirk_flags in snd-usb-audio

[Cryolitia]

> Hello Cryolitia,
> 
> On 2025-09-17 14:46, Cryolitia PukNgae via B4 Relay wrote:
>> From: Cryolitia PukNgae <cryolitia@uniontech.com>
>> 
>> Just briefly described about the new option.
>> 
>> Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com> 

> Isn't the patch subject a bit wrong, and should contain
> "device quirk_flags" instead of "device_device_quirk_flags"?

Sorry for that, I forget to re-write the commit message.
Thx for pointing out.

Best regards,
Cryolitia PukNgae

Re: [PATCH v3 4/4] ALSA: doc: add docs about device_device_quirk_flags in snd-usb-audio

[Randy Dunlap]

On 9/17/25 5:46 AM, Cryolitia PukNgae via B4 Relay wrote:
> @@ -2344,8 +2386,8 @@ report it to the upstream.
>  NB: ``quirk_alias`` option is provided only for testing / development.
>  If you want to have a proper support, contact to upstream for
>  adding the matching quirk in the driver code statically.
> -Ditto for ``quirk_flags``.  If a device is known to require specific
> -workarounds, please report to the upstream.
> +Ditto for ``quirk_flags``.  If a device
> +is known to require specific workarounds, please report to the upstream.

What is the purpose of this change?

-- 
~Randy