Merge tag 'tags/mute-led-rework' into for-next

ALSA: control - add generic LED API

This patchset tries to resolve the diversity in the audio LED
control among the ALSA drivers. A new control layer registration
is introduced which allows to run additional operations on
top of the elementary ALSA sound controls.

A new control access group (three bits in the access flags)
was introduced to carry the LED group information for
the sound controls. The low-level sound drivers can just
mark those controls using this access group. This information
is not exported to the user space, but user space can
manage the LED sound control associations through sysfs
(last patch) per Mark's request. It makes things fully
configurable in the kernel and user space (UCM).

The actual state ('route') evaluation is really easy
(the minimal value check for all channels / controls / cards).
If there's more complicated logic for a given hardware,
the card driver may eventually export a new read-only
sound control for the LED group and do the logic itself.

The new LED trigger control code is completely separated
and possibly optional (there's no symbol dependency).
The full code separation allows eventually to move this
LED trigger control to the user space in future.
Actually it replaces the already present functionality
in the kernel space (HDA drivers) and allows a quick adoption
for the recent hardware (ASoC codecs including SoundWire).

snd_ctl_led            24576  0

The sound driver implementation is really easy:

1) call snd_ctl_led_request() when control LED layer should be
   automatically activated
   / it calls module_request("snd-ctl-led") on demand /
2) mark all related kcontrols with
        SNDRV_CTL_ELEM_ACCESS_SPK_LED or
        SNDRV_CTL_ELEM_ACCESS_MIC_LED

Link: https://lore.kernel.org/r/20210317172945.842280-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

4 files changed, 934 insertions, 26 deletions

diff --git a/sound/core/Kconfig b/sound/core/Kconfig
index a4050f87f230..db2e3c63ff41 100644
--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -203,4 +203,10 @@ config SND_DMA_SGBUF
 	def_bool y
 	depends on X86
 
+config SND_CTL_LED
+	tristate
+	select NEW_LEDS if SND_CTL_LED
+	select LEDS_TRIGGERS if SND_CTL_LED
+	select LEDS_TRIGGER_AUDIO if SND_CTL_LED
+
 source "sound/core/seq/Kconfig"
diff --git a/sound/core/Makefile b/sound/core/Makefile
index ee4a4a6b99ba..d774792850f3 100644
--- a/sound/core/Makefile
+++ b/sound/core/Makefile
@@ -27,6 +27,7 @@ CFLAGS_pcm_native.o := -I$(src)
 
 snd-pcm-dmaengine-objs := pcm_dmaengine.o
 
+snd-ctl-led-objs  := control_led.o
 snd-rawmidi-objs  := rawmidi.o
 snd-timer-objs    := timer.o
 snd-hrtimer-objs  := hrtimer.o
@@ -37,6 +38,7 @@ snd-seq-device-objs := seq_device.o
 snd-compress-objs := compress_offload.o
 
 obj-$(CONFIG_SND) 		+= snd.o
+obj-$(CONFIG_SND_CTL_LED)	+= snd-ctl-led.o
 obj-$(CONFIG_SND_HWDEP)		+= snd-hwdep.o
 obj-$(CONFIG_SND_TIMER)		+= snd-timer.o
 obj-$(CONFIG_SND_HRTIMER)	+= snd-hrtimer.o
diff --git a/sound/core/control.c b/sound/core/control.c
index 5165741a8400..6825ca75daf5 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -28,10 +28,12 @@ struct snd_kctl_ioctl {
 };
 
 static DECLARE_RWSEM(snd_ioctl_rwsem);
+static DECLARE_RWSEM(snd_ctl_layer_rwsem);
 static LIST_HEAD(snd_control_ioctls);
 #ifdef CONFIG_COMPAT
 static LIST_HEAD(snd_control_compat_ioctls);
 #endif
+static struct snd_ctl_layer_ops *snd_ctl_layer;
 
 static int snd_ctl_open(struct inode *inode, struct file *file)
 {
@@ -182,6 +184,32 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,
 EXPORT_SYMBOL(snd_ctl_notify);
 
 /**
+ * snd_ctl_notify_one - Send notification to user-space for a control change
+ * @card: the card to send notification
+ * @mask: the event mask, SNDRV_CTL_EVENT_*
+ * @kctl: the pointer with the control instance
+ * @ioff: the additional offset to the control index
+ *
+ * This function calls snd_ctl_notify() and does additional jobs
+ * like LED state changes.
+ */
+void snd_ctl_notify_one(struct snd_card *card, unsigned int mask,
+			struct snd_kcontrol *kctl, unsigned int ioff)
+{
+	struct snd_ctl_elem_id id = kctl->id;
+	struct snd_ctl_layer_ops *lops;
+
+	id.index += ioff;
+	id.numid += ioff;
+	snd_ctl_notify(card, mask, &id);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->lnotify(card, mask, kctl, ioff);
+	up_read(&snd_ctl_layer_rwsem);
+}
+EXPORT_SYMBOL(snd_ctl_notify_one);
+
+/**
  * snd_ctl_new - create a new control instance with some elements
  * @kctl: the pointer to store new control instance
  * @count: the number of elements in this control
@@ -250,6 +278,7 @@ struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol,
 		   SNDRV_CTL_ELEM_ACCESS_TLV_READWRITE |
 		   SNDRV_CTL_ELEM_ACCESS_TLV_COMMAND |
 		   SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK |
+		   SNDRV_CTL_ELEM_ACCESS_LED_MASK |
 		   SNDRV_CTL_ELEM_ACCESS_SKIP_CHECK);
 
 	err = snd_ctl_new(&kctl, count, access, NULL);
@@ -342,7 +371,6 @@ static int __snd_ctl_add_replace(struct snd_card *card,
 {
 	struct snd_ctl_elem_id id;
 	unsigned int idx;
-	unsigned int count;
 	struct snd_kcontrol *old;
 	int err;
 
@@ -376,10 +404,8 @@ static int __snd_ctl_add_replace(struct snd_card *card,
 	kcontrol->id.numid = card->last_numid + 1;
 	card->last_numid += kcontrol->count;
 
-	id = kcontrol->id;
-	count = kcontrol->count;
-	for (idx = 0; idx < count; idx++, id.index++, id.numid++)
-		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
+	for (idx = 0; idx < kcontrol->count; idx++)
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_ADD, kcontrol, idx);
 
 	return 0;
 }
@@ -462,16 +488,14 @@ EXPORT_SYMBOL(snd_ctl_replace);
  */
 int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
 {
-	struct snd_ctl_elem_id id;
 	unsigned int idx;
 
 	if (snd_BUG_ON(!card || !kcontrol))
 		return -EINVAL;
 	list_del(&kcontrol->list);
 	card->controls_count -= kcontrol->count;
-	id = kcontrol->id;
-	for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
-		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_REMOVE, &id);
+	for (idx = 0; idx < kcontrol->count; idx++)
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_REMOVE, kcontrol, idx);
 	snd_ctl_free_one(kcontrol);
 	return 0;
 }
@@ -584,11 +608,13 @@ int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
 		vd->access |= SNDRV_CTL_ELEM_ACCESS_INACTIVE;
 	}
 	snd_ctl_build_ioff(id, kctl, index_offset);
-	ret = 1;
+	downgrade_write(&card->controls_rwsem);
+	snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_INFO, kctl, index_offset);
+	up_read(&card->controls_rwsem);
+	return 1;
+
  unlock:
 	up_write(&card->controls_rwsem);
-	if (ret > 0)
-		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO, id);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(snd_ctl_activate_id);
@@ -1022,7 +1048,8 @@ static int snd_ctl_elem_info_user(struct snd_ctl_file *ctl,
 	if (result < 0)
 		return result;
 	/* drop internal access flags */
-	info.access &= ~SNDRV_CTL_ELEM_ACCESS_SKIP_CHECK;
+	info.access &= ~(SNDRV_CTL_ELEM_ACCESS_SKIP_CHECK|
+			 SNDRV_CTL_ELEM_ACCESS_LED_MASK);
 	if (copy_to_user(_info, &info, sizeof(info)))
 		return -EFAULT;
 	return result;
@@ -1110,25 +1137,34 @@ static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
 	unsigned int index_offset;
 	int result;
 
+	down_write(&card->controls_rwsem);
 	kctl = snd_ctl_find_id(card, &control->id);
-	if (kctl == NULL)
+	if (kctl == NULL) {
+		up_write(&card->controls_rwsem);
 		return -ENOENT;
+	}
 
 	index_offset = snd_ctl_get_ioff(kctl, &control->id);
 	vd = &kctl->vd[index_offset];
 	if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) || kctl->put == NULL ||
 	    (file && vd->owner && vd->owner != file)) {
+		up_write(&card->controls_rwsem);
 		return -EPERM;
 	}
 
 	snd_ctl_build_ioff(&control->id, kctl, index_offset);
 	result = kctl->put(kctl, control);
-	if (result < 0)
+	if (result < 0) {
+		up_write(&card->controls_rwsem);
 		return result;
+	}
 
 	if (result > 0) {
-		struct snd_ctl_elem_id id = control->id;
-		snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id);
+		downgrade_write(&card->controls_rwsem);
+		snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_VALUE, kctl, index_offset);
+		up_read(&card->controls_rwsem);
+	} else {
+		up_write(&card->controls_rwsem);
 	}
 
 	return 0;
@@ -1150,9 +1186,7 @@ static int snd_ctl_elem_write_user(struct snd_ctl_file *file,
 	if (result < 0)
 		goto error;
 
-	down_write(&card->controls_rwsem);
 	result = snd_ctl_elem_write(card, file, control);
-	up_write(&card->controls_rwsem);
 	if (result < 0)
 		goto error;
 
@@ -1301,7 +1335,6 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
 {
 	struct user_element *ue = kctl->private_data;
 	unsigned int *container;
-	struct snd_ctl_elem_id id;
 	unsigned int mask = 0;
 	int i;
 	int change;
@@ -1333,10 +1366,8 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf,
 	ue->tlv_data_size = size;
 
 	mask |= SNDRV_CTL_EVENT_MASK_TLV;
-	for (i = 0; i < kctl->count; ++i) {
-		snd_ctl_build_ioff(&id, kctl, i);
-		snd_ctl_notify(ue->card, mask, &id);
-	}
+	for (i = 0; i < kctl->count; ++i)
+		snd_ctl_notify_one(ue->card, mask, kctl, i);
 
 	return change;
 }
@@ -1976,6 +2007,86 @@ EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
 #endif
 
 /*
+ * control layers (audio LED etc.)
+ */
+
+/**
+ * snd_ctl_request_layer - request to use the layer
+ * @module_name: Name of the kernel module (NULL == build-in)
+ *
+ * Return an error code when the module cannot be loaded.
+ */
+int snd_ctl_request_layer(const char *module_name)
+{
+	struct snd_ctl_layer_ops *lops;
+
+	if (module_name == NULL)
+		return 0;
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		if (strcmp(lops->module_name, module_name) == 0)
+			break;
+	up_read(&snd_ctl_layer_rwsem);
+	if (lops)
+		return 0;
+	return request_module(module_name);
+}
+EXPORT_SYMBOL_GPL(snd_ctl_request_layer);
+
+/**
+ * snd_ctl_register_layer - register new control layer
+ * @lops: operation structure
+ *
+ * The new layer can track all control elements and do additional
+ * operations on top (like audio LED handling).
+ */
+void snd_ctl_register_layer(struct snd_ctl_layer_ops *lops)
+{
+	struct snd_card *card;
+	int card_number;
+
+	down_write(&snd_ctl_layer_rwsem);
+	lops->next = snd_ctl_layer;
+	snd_ctl_layer = lops;
+	up_write(&snd_ctl_layer_rwsem);
+	for (card_number = 0; card_number < SNDRV_CARDS; card_number++) {
+		card = snd_card_ref(card_number);
+		if (card) {
+			down_read(&card->controls_rwsem);
+			lops->lregister(card);
+			up_read(&card->controls_rwsem);
+			snd_card_unref(card);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(snd_ctl_register_layer);
+
+/**
+ * snd_ctl_disconnect_layer - disconnect control layer
+ * @lops: operation structure
+ *
+ * It is expected that the information about tracked cards
+ * is freed before this call (the disconnect callback is
+ * not called here).
+ */
+void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
+{
+	struct snd_ctl_layer_ops *lops2, *prev_lops2;
+
+	down_write(&snd_ctl_layer_rwsem);
+	for (lops2 = snd_ctl_layer, prev_lops2 = NULL; lops2; lops2 = lops2->next)
+		if (lops2 == lops) {
+			if (!prev_lops2)
+				snd_ctl_layer = lops->next;
+			else
+				prev_lops2->next = lops->next;
+			break;
+		}
+	up_write(&snd_ctl_layer_rwsem);
+}
+EXPORT_SYMBOL_GPL(snd_ctl_disconnect_layer);
+
+/*
  *  INIT PART
  */
 
@@ -1998,9 +2109,20 @@ static const struct file_operations snd_ctl_f_ops =
 static int snd_ctl_dev_register(struct snd_device *device)
 {
 	struct snd_card *card = device->device_data;
+	struct snd_ctl_layer_ops *lops;
+	int err;
 
-	return snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
-				   &snd_ctl_f_ops, card, &card->ctl_dev);
+	err = snd_register_device(SNDRV_DEVICE_TYPE_CONTROL, card, -1,
+				  &snd_ctl_f_ops, card, &card->ctl_dev);
+	if (err < 0)
+		return err;
+	down_read(&card->controls_rwsem);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->lregister(card);
+	up_read(&snd_ctl_layer_rwsem);
+	up_read(&card->controls_rwsem);
+	return 0;
 }
 
 /*
@@ -2010,6 +2132,7 @@ static int snd_ctl_dev_disconnect(struct snd_device *device)
 {
 	struct snd_card *card = device->device_data;
 	struct snd_ctl_file *ctl;
+	struct snd_ctl_layer_ops *lops;
 	unsigned long flags;
 
 	read_lock_irqsave(&card->ctl_files_rwlock, flags);
@@ -2019,6 +2142,13 @@ static int snd_ctl_dev_disconnect(struct snd_device *device)
 	}
 	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
 
+	down_read(&card->controls_rwsem);
+	down_read(&snd_ctl_layer_rwsem);
+	for (lops = snd_ctl_layer; lops; lops = lops->next)
+		lops->ldisconnect(card);
+	up_read(&snd_ctl_layer_rwsem);
+	up_read(&card->controls_rwsem);
+
 	return snd_unregister_device(&card->ctl_dev);
 }
 
diff --git a/sound/core/control_led.c b/sound/core/control_led.c
new file mode 100644
index 000000000000..d4fb8b873f34
--- /dev/null
+++ b/sound/core/control_led.c
@@ -0,0 +1,770 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  LED state routines for driver control interface
+ *  Copyright (c) 2021 by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/leds.h>
+#include <sound/core.h>
+#include <sound/control.h>
+
+MODULE_AUTHOR("Jaroslav Kysela <perex@perex.cz>");
+MODULE_DESCRIPTION("ALSA control interface to LED trigger code.");
+MODULE_LICENSE("GPL");
+
+#define MAX_LED (((SNDRV_CTL_ELEM_ACCESS_MIC_LED - SNDRV_CTL_ELEM_ACCESS_SPK_LED) \
+			>> SNDRV_CTL_ELEM_ACCESS_LED_SHIFT) + 1)
+
+enum snd_ctl_led_mode {
+	 MODE_FOLLOW_MUTE = 0,
+	 MODE_FOLLOW_ROUTE,
+	 MODE_OFF,
+	 MODE_ON,
+};
+
+struct snd_ctl_led_card {
+	struct device dev;
+	int number;
+	struct snd_ctl_led *led;
+};
+
+struct snd_ctl_led {
+	struct device dev;
+	struct list_head controls;
+	const char *name;
+	unsigned int group;
+	enum led_audio trigger_type;
+	enum snd_ctl_led_mode mode;
+	struct snd_ctl_led_card *cards[SNDRV_CARDS];
+};
+
+struct snd_ctl_led_ctl {
+	struct list_head list;
+	struct snd_card *card;
+	unsigned int access;
+	struct snd_kcontrol *kctl;
+	unsigned int index_offset;
+};
+
+static DEFINE_MUTEX(snd_ctl_led_mutex);
+static bool snd_ctl_led_card_valid[SNDRV_CARDS];
+static struct snd_ctl_led snd_ctl_leds[MAX_LED] = {
+	{
+		.name = "speaker",
+		.group = (SNDRV_CTL_ELEM_ACCESS_SPK_LED >> SNDRV_CTL_ELEM_ACCESS_LED_SHIFT) - 1,
+		.trigger_type = LED_AUDIO_MUTE,
+		.mode = MODE_FOLLOW_MUTE,
+	},
+	{
+		.name = "mic",
+		.group = (SNDRV_CTL_ELEM_ACCESS_MIC_LED >> SNDRV_CTL_ELEM_ACCESS_LED_SHIFT) - 1,
+		.trigger_type = LED_AUDIO_MICMUTE,
+		.mode = MODE_FOLLOW_MUTE,
+	},
+};
+
+static void snd_ctl_led_sysfs_add(struct snd_card *card);
+static void snd_ctl_led_sysfs_remove(struct snd_card *card);
+
+#define UPDATE_ROUTE(route, cb) \
+	do { \
+		int route2 = (cb); \
+		if (route2 >= 0) \
+			route = route < 0 ? route2 : (route | route2); \
+	} while (0)
+
+static inline unsigned int access_to_group(unsigned int access)
+{
+	return ((access & SNDRV_CTL_ELEM_ACCESS_LED_MASK) >>
+				SNDRV_CTL_ELEM_ACCESS_LED_SHIFT) - 1;
+}
+
+static inline unsigned int group_to_access(unsigned int group)
+{
+	return (group + 1) << SNDRV_CTL_ELEM_ACCESS_LED_SHIFT;
+}
+
+static struct snd_ctl_led *snd_ctl_led_get_by_access(unsigned int access)
+{
+	unsigned int group = access_to_group(access);
+	if (group >= MAX_LED)
+		return NULL;
+	return &snd_ctl_leds[group];
+}
+
+static int snd_ctl_led_get(struct snd_ctl_led_ctl *lctl)
+{
+	struct snd_kcontrol *kctl = lctl->kctl;
+	struct snd_ctl_elem_info info;
+	struct snd_ctl_elem_value value;
+	unsigned int i;
+	int result;
+
+	memset(&info, 0, sizeof(info));
+	info.id = kctl->id;
+	info.id.index += lctl->index_offset;
+	info.id.numid += lctl->index_offset;
+	result = kctl->info(kctl, &info);
+	if (result < 0)
+		return -1;
+	memset(&value, 0, sizeof(value));
+	value.id = info.id;
+	result = kctl->get(kctl, &value);
+	if (result < 0)
+		return -1;
+	if (info.type == SNDRV_CTL_ELEM_TYPE_BOOLEAN ||
+	    info.type == SNDRV_CTL_ELEM_TYPE_INTEGER) {
+		for (i = 0; i < info.count; i++)
+			if (value.value.integer.value[i] != info.value.integer.min)
+				return 1;
+	} else if (info.type == SNDRV_CTL_ELEM_TYPE_INTEGER64) {
+		for (i = 0; i < info.count; i++)
+			if (value.value.integer64.value[i] != info.value.integer64.min)
+				return 1;
+	}
+	return 0;
+}
+
+static void snd_ctl_led_set_state(struct snd_card *card, unsigned int access,
+				  struct snd_kcontrol *kctl, unsigned int ioff)
+{
+	struct snd_ctl_led *led;
+	struct snd_ctl_led_ctl *lctl;
+	int route;
+	bool found;
+
+	led = snd_ctl_led_get_by_access(access);
+	if (!led)
+		return;
+	route = -1;
+	found = false;
+	mutex_lock(&snd_ctl_led_mutex);
+	/* the card may not be registered (active) at this point */
+	if (card && !snd_ctl_led_card_valid[card->number]) {
+		mutex_unlock(&snd_ctl_led_mutex);
+		return;
+	}
+	list_for_each_entry(lctl, &led->controls, list) {
+		if (lctl->kctl == kctl && lctl->index_offset == ioff)
+			found = true;
+		UPDATE_ROUTE(route, snd_ctl_led_get(lctl));
+	}
+	if (!found && kctl && card) {
+		lctl = kzalloc(sizeof(*lctl), GFP_KERNEL);
+		if (lctl) {
+			lctl->card = card;
+			lctl->access = access;
+			lctl->kctl = kctl;
+			lctl->index_offset = ioff;
+			list_add(&lctl->list, &led->controls);
+			UPDATE_ROUTE(route, snd_ctl_led_get(lctl));
+		}
+	}
+	mutex_unlock(&snd_ctl_led_mutex);
+	switch (led->mode) {
+	case MODE_OFF:		route = 1; break;
+	case MODE_ON:		route = 0; break;
+	case MODE_FOLLOW_ROUTE:	if (route >= 0) route ^= 1; break;
+	case MODE_FOLLOW_MUTE:	/* noop */ break;
+	}
+	if (route >= 0)
+		ledtrig_audio_set(led->trigger_type, route ? LED_OFF : LED_ON);
+}
+
+static struct snd_ctl_led_ctl *snd_ctl_led_find(struct snd_kcontrol *kctl, unsigned int ioff)
+{
+	struct list_head *controls;
+	struct snd_ctl_led_ctl *lctl;
+	unsigned int group;
+
+	for (group = 0; group < MAX_LED; group++) {
+		controls = &snd_ctl_leds[group].controls;
+		list_for_each_entry(lctl, controls, list)
+			if (lctl->kctl == kctl && lctl->index_offset == ioff)
+				return lctl;
+	}
+	return NULL;
+}
+
+static unsigned int snd_ctl_led_remove(struct snd_kcontrol *kctl, unsigned int ioff,
+				       unsigned int access)
+{
+	struct snd_ctl_led_ctl *lctl;
+	unsigned int ret = 0;
+
+	mutex_lock(&snd_ctl_led_mutex);
+	lctl = snd_ctl_led_find(kctl, ioff);
+	if (lctl && (access == 0 || access != lctl->access)) {
+		ret = lctl->access;
+		list_del(&lctl->list);
+		kfree(lctl);
+	}
+	mutex_unlock(&snd_ctl_led_mutex);
+	return ret;
+}
+
+static void snd_ctl_led_notify(struct snd_card *card, unsigned int mask,
+			       struct snd_kcontrol *kctl, unsigned int ioff)
+{
+	struct snd_kcontrol_volatile *vd;
+	unsigned int access, access2;
+
+	if (mask == SNDRV_CTL_EVENT_MASK_REMOVE) {
+		access = snd_ctl_led_remove(kctl, ioff, 0);
+		if (access)
+			snd_ctl_led_set_state(card, access, NULL, 0);
+	} else if (mask & SNDRV_CTL_EVENT_MASK_INFO) {
+		vd = &kctl->vd[ioff];
+		access = vd->access & SNDRV_CTL_ELEM_ACCESS_LED_MASK;
+		access2 = snd_ctl_led_remove(kctl, ioff, access);
+		if (access2)
+			snd_ctl_led_set_state(card, access2, NULL, 0);
+		if (access)
+			snd_ctl_led_set_state(card, access, kctl, ioff);
+	} else if ((mask & (SNDRV_CTL_EVENT_MASK_ADD |
+			    SNDRV_CTL_EVENT_MASK_VALUE)) != 0) {
+		vd = &kctl->vd[ioff];
+		access = vd->access & SNDRV_CTL_ELEM_ACCESS_LED_MASK;
+		if (access)
+			snd_ctl_led_set_state(card, access, kctl, ioff);
+	}
+}
+
+static int snd_ctl_led_set_id(int card_number, struct snd_ctl_elem_id *id,
+			      unsigned int group, bool set)
+{
+	struct snd_card *card;
+	struct snd_kcontrol *kctl;
+	struct snd_kcontrol_volatile *vd;
+	unsigned int ioff, access, new_access;
+	int err = 0;
+
+	card = snd_card_ref(card_number);
+	if (card) {
+		down_write(&card->controls_rwsem);
+		kctl = snd_ctl_find_id(card, id);
+		if (kctl) {
+			ioff = snd_ctl_get_ioff(kctl, id);
+			vd = &kctl->vd[ioff];
+			access = vd->access & SNDRV_CTL_ELEM_ACCESS_LED_MASK;
+			if (access != 0 && access != group_to_access(group)) {
+				err = -EXDEV;
+				goto unlock;
+			}
+			new_access = vd->access & ~SNDRV_CTL_ELEM_ACCESS_LED_MASK;
+			if (set)
+				new_access |= group_to_access(group);
+			if (new_access != vd->access) {
+				vd->access = new_access;
+				snd_ctl_led_notify(card, SNDRV_CTL_EVENT_MASK_INFO, kctl, ioff);
+			}
+		} else {
+			err = -ENOENT;
+		}
+unlock:
+		up_write(&card->controls_rwsem);
+		snd_card_unref(card);
+	} else {
+		err = -ENXIO;
+	}
+	return err;
+}
+
+static void snd_ctl_led_refresh(void)
+{
+	unsigned int group;
+
+	for (group = 0; group < MAX_LED; group++)
+		snd_ctl_led_set_state(NULL, group_to_access(group), NULL, 0);
+}
+
+static void snd_ctl_led_ctl_destroy(struct snd_ctl_led_ctl *lctl)
+{
+	list_del(&lctl->list);
+	kfree(lctl);
+}
+
+static void snd_ctl_led_clean(struct snd_card *card)
+{
+	unsigned int group;
+	struct snd_ctl_led *led;
+	struct snd_ctl_led_ctl *lctl;
+
+	for (group = 0; group < MAX_LED; group++) {
+		led = &snd_ctl_leds[group];
+repeat:
+		list_for_each_entry(lctl, &led->controls, list)
+			if (!card || lctl->card == card) {
+				snd_ctl_led_ctl_destroy(lctl);
+				goto repeat;
+			}
+	}
+}
+
+static int snd_ctl_led_reset(int card_number, unsigned int group)
+{
+	struct snd_card *card;
+	struct snd_ctl_led *led;
+	struct snd_ctl_led_ctl *lctl;
+	struct snd_kcontrol_volatile *vd;
+	bool change = false;
+
+	card = snd_card_ref(card_number);
+	if (!card)
+		return -ENXIO;
+
+	mutex_lock(&snd_ctl_led_mutex);
+	if (!snd_ctl_led_card_valid[card_number]) {
+		mutex_unlock(&snd_ctl_led_mutex);
+		snd_card_unref(card);
+		return -ENXIO;
+	}
+	led = &snd_ctl_leds[group];
+repeat:
+	list_for_each_entry(lctl, &led->controls, list)
+		if (lctl->card == card) {
+			vd = &lctl->kctl->vd[lctl->index_offset];
+			vd->access &= ~group_to_access(group);
+			snd_ctl_led_ctl_destroy(lctl);
+			change = true;
+			goto repeat;
+		}
+	mutex_unlock(&snd_ctl_led_mutex);
+	if (change)
+		snd_ctl_led_set_state(NULL, group_to_access(group), NULL, 0);
+	snd_card_unref(card);
+	return 0;
+}
+
+static void snd_ctl_led_register(struct snd_card *card)
+{
+	struct snd_kcontrol *kctl;
+	unsigned int ioff;
+
+	if (snd_BUG_ON(card->number < 0 ||
+		       card->number >= ARRAY_SIZE(snd_ctl_led_card_valid)))
+		return;
+	mutex_lock(&snd_ctl_led_mutex);
+	snd_ctl_led_card_valid[card->number] = true;
+	mutex_unlock(&snd_ctl_led_mutex);
+	/* the register callback is already called with held card->controls_rwsem */
+	list_for_each_entry(kctl, &card->controls, list)
+		for (ioff = 0; ioff < kctl->count; ioff++)
+			snd_ctl_led_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, kctl, ioff);
+	snd_ctl_led_refresh();
+	snd_ctl_led_sysfs_add(card);
+}
+
+static void snd_ctl_led_disconnect(struct snd_card *card)
+{
+	snd_ctl_led_sysfs_remove(card);
+	mutex_lock(&snd_ctl_led_mutex);
+	snd_ctl_led_card_valid[card->number] = false;
+	snd_ctl_led_clean(card);
+	mutex_unlock(&snd_ctl_led_mutex);
+	snd_ctl_led_refresh();
+}
+
+/*
+ * sysfs
+ */
+
+static ssize_t show_mode(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct snd_ctl_led *led = container_of(dev, struct snd_ctl_led, dev);
+	const char *str;
+
+	switch (led->mode) {
+	case MODE_FOLLOW_MUTE:	str = "follow-mute"; break;
+	case MODE_FOLLOW_ROUTE:	str = "follow-route"; break;
+	case MODE_ON:		str = "on"; break;
+	case MODE_OFF:		str = "off"; break;
+	}
+	return sprintf(buf, "%s\n", str);
+}
+
+static ssize_t store_mode(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct snd_ctl_led *led = container_of(dev, struct snd_ctl_led, dev);
+	char _buf[16];
+	size_t l = min(count, sizeof(_buf) - 1) + 1;
+	enum snd_ctl_led_mode mode;
+
+	memcpy(_buf, buf, l);
+	_buf[l] = '\0';
+	if (strstr(_buf, "mute"))
+		mode = MODE_FOLLOW_MUTE;
+	else if (strstr(_buf, "route"))
+		mode = MODE_FOLLOW_ROUTE;
+	else if (strncmp(_buf, "off", 3) == 0 || strncmp(_buf, "0", 1) == 0)
+		mode = MODE_OFF;
+	else if (strncmp(_buf, "on", 2) == 0 || strncmp(_buf, "1", 1) == 0)
+		mode = MODE_ON;
+	else
+		return count;
+
+	mutex_lock(&snd_ctl_led_mutex);
+	led->mode = mode;
+	mutex_unlock(&snd_ctl_led_mutex);
+
+	snd_ctl_led_set_state(NULL, group_to_access(led->group), NULL, 0);
+	return count;
+}
+
+static ssize_t show_brightness(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct snd_ctl_led *led = container_of(dev, struct snd_ctl_led, dev);
+
+	return sprintf(buf, "%u\n", ledtrig_audio_get(led->trigger_type));
+}
+
+static DEVICE_ATTR(mode, 0644, show_mode, store_mode);
+static DEVICE_ATTR(brightness, 0444, show_brightness, NULL);
+
+static struct attribute *snd_ctl_led_dev_attrs[] = {
+	&dev_attr_mode.attr,
+	&dev_attr_brightness.attr,
+	NULL,
+};
+
+static const struct attribute_group snd_ctl_led_dev_attr_group = {
+	.attrs = snd_ctl_led_dev_attrs,
+};
+
+static const struct attribute_group *snd_ctl_led_dev_attr_groups[] = {
+	&snd_ctl_led_dev_attr_group,
+	NULL,
+};
+
+static char *find_eos(char *s)
+{
+	while (*s && *s != ',')
+		s++;
+	if (*s)
+		s++;
+	return s;
+}
+
+static char *parse_uint(char *s, unsigned int *val)
+{
+	unsigned long long res;
+	if (kstrtoull(s, 10, &res))
+		res = 0;
+	*val = res;
+	return find_eos(s);
+}
+
+static char *parse_string(char *s, char *val, size_t val_size)
+{
+	if (*s == '"' || *s == '\'') {
+		char c = *s;
+		s++;
+		while (*s && *s != c) {
+			if (val_size > 1) {
+				*val++ = *s;
+				val_size--;
+			}
+			s++;
+		}
+	} else {
+		while (*s && *s != ',') {
+			if (val_size > 1) {
+				*val++ = *s;
+				val_size--;
+			}
+			s++;
+		}
+	}
+	*val = '\0';
+	if (*s)
+		s++;
+	return s;
+}
+
+static char *parse_iface(char *s, unsigned int *val)
+{
+	if (!strncasecmp(s, "card", 4))
+		*val = SNDRV_CTL_ELEM_IFACE_CARD;
+	else if (!strncasecmp(s, "mixer", 5))
+		*val = SNDRV_CTL_ELEM_IFACE_MIXER;
+	return find_eos(s);
+}
+
+/*
+ * These types of input strings are accepted:
+ *
+ *   unsigned integer - numid (equivaled to numid=UINT)
+ *   string - basic mixer name (equivalent to iface=MIXER,name=STR)
+ *   numid=UINT
+ *   [iface=MIXER,][device=UINT,][subdevice=UINT,]name=STR[,index=UINT]
+ */
+static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, size_t count,
+			  bool attach)
+{
+	char buf2[256], *s;
+	size_t len = max(sizeof(s) - 1, count);
+	struct snd_ctl_elem_id id;
+	int err;
+
+	strncpy(buf2, buf, len);
+	buf2[len] = '\0';
+	memset(&id, 0, sizeof(id));
+	id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
+	s = buf2;
+	while (*s) {
+		if (!strncasecmp(s, "numid=", 6)) {
+			s = parse_uint(s + 6, &id.numid);
+		} else if (!strncasecmp(s, "iface=", 6)) {
+			s = parse_iface(s + 6, &id.iface);
+		} else if (!strncasecmp(s, "device=", 7)) {
+			s = parse_uint(s + 7, &id.device);
+		} else if (!strncasecmp(s, "subdevice=", 10)) {
+			s = parse_uint(s + 10, &id.subdevice);
+		} else if (!strncasecmp(s, "name=", 5)) {
+			s = parse_string(s + 5, id.name, sizeof(id.name));
+		} else if (!strncasecmp(s, "index=", 6)) {
+			s = parse_uint(s + 6, &id.index);
+		} else if (s == buf2) {
+			while (*s) {
+				if (*s < '0' || *s > '9')
+					break;
+				s++;
+			}
+			if (*s == '\0')
+				parse_uint(buf2, &id.numid);
+			else {
+				for (; *s >= ' '; s++);
+				*s = '\0';
+				strlcpy(id.name, buf2, sizeof(id.name));
+			}
+			break;
+		}
+		if (*s == ',')
+			s++;
+	}
+
+	err = snd_ctl_led_set_id(led_card->number, &id, led_card->led->group, attach);
+	if (err < 0)
+		return err;
+
+	return count;
+}
+
+static ssize_t parse_attach(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev);
+	return set_led_id(led_card, buf, count, true);
+}
+
+static ssize_t parse_detach(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev);
+	return set_led_id(led_card, buf, count, false);
+}
+
+static ssize_t ctl_reset(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev);
+	int err;
+
+	if (count > 0 && buf[0] == '1') {
+		err = snd_ctl_led_reset(led_card->number, led_card->led->group);
+		if (err < 0)
+			return err;
+	}
+	return count;
+}
+
+static ssize_t ctl_list(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct snd_ctl_led_card *led_card = container_of(dev, struct snd_ctl_led_card, dev);
+	struct snd_card *card;
+	struct snd_ctl_led_ctl *lctl;
+	char *buf2 = buf;
+	size_t l;
+
+	card = snd_card_ref(led_card->number);
+	if (!card)
+		return -ENXIO;
+	down_read(&card->controls_rwsem);
+	mutex_lock(&snd_ctl_led_mutex);
+	if (snd_ctl_led_card_valid[led_card->number]) {
+		list_for_each_entry(lctl, &led_card->led->controls, list)
+			if (lctl->card == card) {
+				if (buf2 - buf > PAGE_SIZE - 16)
+					break;
+				if (buf2 != buf)
+					*buf2++ = ' ';
+				l = scnprintf(buf2, 15, "%u",
+						lctl->kctl->id.numid +
+							lctl->index_offset);
+				buf2[l] = '\0';
+				buf2 += l + 1;
+			}
+	}
+	mutex_unlock(&snd_ctl_led_mutex);
+	up_read(&card->controls_rwsem);
+	snd_card_unref(card);
+	return buf2 - buf;
+}
+
+static DEVICE_ATTR(attach, 0200, NULL, parse_attach);
+static DEVICE_ATTR(detach, 0200, NULL, parse_detach);
+static DEVICE_ATTR(reset, 0200, NULL, ctl_reset);
+static DEVICE_ATTR(list, 0444, ctl_list, NULL);
+
+static struct attribute *snd_ctl_led_card_attrs[] = {
+	&dev_attr_attach.attr,
+	&dev_attr_detach.attr,
+	&dev_attr_reset.attr,
+	&dev_attr_list.attr,
+	NULL,
+};
+
+static const struct attribute_group snd_ctl_led_card_attr_group = {
+	.attrs = snd_ctl_led_card_attrs,
+};
+
+static const struct attribute_group *snd_ctl_led_card_attr_groups[] = {
+	&snd_ctl_led_card_attr_group,
+	NULL,
+};
+
+static struct device snd_ctl_led_dev;
+
+static void snd_ctl_led_sysfs_add(struct snd_card *card)
+{
+	unsigned int group;
+	struct snd_ctl_led_card *led_card;
+	struct snd_ctl_led *led;
+	char link_name[32];
+
+	for (group = 0; group < MAX_LED; group++) {
+		led = &snd_ctl_leds[group];
+		led_card = kzalloc(sizeof(*led_card), GFP_KERNEL);
+		if (!led_card)
+			goto cerr2;
+		led_card->number = card->number;
+		led_card->led = led;
+		device_initialize(&led_card->dev);
+		if (dev_set_name(&led_card->dev, "card%d", card->number) < 0)
+			goto cerr;
+		led_card->dev.parent = &led->dev;
+		led_card->dev.groups = snd_ctl_led_card_attr_groups;
+		if (device_add(&led_card->dev))
+			goto cerr;
+		led->cards[card->number] = led_card;
+		snprintf(link_name, sizeof(link_name), "led-%s", led->name);
+		WARN(sysfs_create_link(&card->ctl_dev.kobj, &led_card->dev.kobj, link_name),
+			"can't create symlink to controlC%i device\n", card->number);
+		WARN(sysfs_create_link(&led_card->dev.kobj, &card->card_dev.kobj, "card"),
+			"can't create symlink to card%i\n", card->number);
+
+		continue;
+cerr:
+		put_device(&led_card->dev);
+cerr2:
+		printk(KERN_ERR "snd_ctl_led: unable to add card%d", card->number);
+		kfree(led_card);
+	}
+}
+
+static void snd_ctl_led_sysfs_remove(struct snd_card *card)
+{
+	unsigned int group;
+	struct snd_ctl_led_card *led_card;
+	struct snd_ctl_led *led;
+	char link_name[32];
+
+	for (group = 0; group < MAX_LED; group++) {
+		led = &snd_ctl_leds[group];
+		led_card = led->cards[card->number];
+		if (!led_card)
+			continue;
+		snprintf(link_name, sizeof(link_name), "led-%s", led->name);
+		sysfs_remove_link(&card->ctl_dev.kobj, link_name);
+		sysfs_remove_link(&led_card->dev.kobj, "card");
+		device_del(&led_card->dev);
+		kfree(led_card);
+		led->cards[card->number] = NULL;
+	}
+}
+
+/*
+ * Control layer registration
+ */
+static struct snd_ctl_layer_ops snd_ctl_led_lops = {
+	.module_name = SND_CTL_LAYER_MODULE_LED,
+	.lregister = snd_ctl_led_register,
+	.ldisconnect = snd_ctl_led_disconnect,
+	.lnotify = snd_ctl_led_notify,
+};
+
+static int __init snd_ctl_led_init(void)
+{
+	struct snd_ctl_led *led;
+	unsigned int group;
+
+	device_initialize(&snd_ctl_led_dev);
+	snd_ctl_led_dev.class = sound_class;
+	dev_set_name(&snd_ctl_led_dev, "ctl-led");
+	if (device_add(&snd_ctl_led_dev)) {
+		put_device(&snd_ctl_led_dev);
+		return -ENOMEM;
+	}
+	for (group = 0; group < MAX_LED; group++) {
+		led = &snd_ctl_leds[group];
+		INIT_LIST_HEAD(&led->controls);
+		device_initialize(&led->dev);
+		led->dev.parent = &snd_ctl_led_dev;
+		led->dev.groups = snd_ctl_led_dev_attr_groups;
+		dev_set_name(&led->dev, led->name);
+		if (device_add(&led->dev)) {
+			put_device(&led->dev);
+			for (; group > 0; group--) {
+				led = &snd_ctl_leds[group];
+				device_del(&led->dev);
+			}
+			device_del(&snd_ctl_led_dev);
+			return -ENOMEM;
+		}
+	}
+	snd_ctl_register_layer(&snd_ctl_led_lops);
+	return 0;
+}
+
+static void __exit snd_ctl_led_exit(void)
+{
+	struct snd_ctl_led *led;
+	struct snd_card *card;
+	unsigned int group, card_number;
+
+	snd_ctl_disconnect_layer(&snd_ctl_led_lops);
+	for (card_number = 0; card_number < SNDRV_CARDS; card_number++) {
+		if (!snd_ctl_led_card_valid[card_number])
+			continue;
+		card = snd_card_ref(card_number);
+		if (card) {
+			snd_ctl_led_sysfs_remove(card);
+			snd_card_unref(card);
+		}
+	}
+	for (group = 0; group < MAX_LED; group++) {
+		led = &snd_ctl_leds[group];
+		device_del(&led->dev);
+	}
+	device_del(&snd_ctl_led_dev);
+	snd_ctl_led_clean(NULL);
+}
+
+module_init(snd_ctl_led_init)
+module_exit(snd_ctl_led_exit)