ALSA: bebob: Prepare for device specific operations

This commit is for some devices which have its own operations or quirks.

Many functionality should be implemented in user land. Then this commit adds
functionality related to stream such as sampling frequency or clock source. For
help to debug, this commit adds the functionality to get metering information
if it's available.

To help these functionalities, this commit adds some AV/C commands defined in
'AV/C Audio Subunit Specification (1394TA).

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

7 files changed, 230 insertions, 42 deletions

diff --git a/sound/firewire/bebob/Makefile b/sound/firewire/bebob/Makefile
index 7808777..e4b08e3 100644
--- a/sound/firewire/bebob/Makefile
+++ b/sound/firewire/bebob/Makefile
@@ -1,4 +1,3 @@
 snd-bebob-objs := bebob_command.o bebob_stream.o bebob_proc.o bebob_midi.o \
-		  bebob_pcm.o bebob_hwdep.o \
-		  bebob.o
+		  bebob_pcm.o bebob_hwdep.o bebob.o
 obj-m += snd-bebob.o
diff --git a/sound/firewire/bebob/bebob.c b/sound/firewire/bebob/bebob.c
index b7d70c2..3d79090 100644
--- a/sound/firewire/bebob/bebob.c
+++ b/sound/firewire/bebob/bebob.c
@@ -126,6 +126,7 @@ bebob_probe(struct fw_unit *unit,
 {
 	struct snd_card *card;
 	struct snd_bebob *bebob;
+	const struct snd_bebob_spec *spec;
 	unsigned int card_index;
 	int err;
 
@@ -140,6 +141,12 @@ bebob_probe(struct fw_unit *unit,
 		goto end;
 	}
 
+	spec = (const struct snd_bebob_spec *)entry->driver_data;
+	if (spec == NULL) {
+		err = -ENOSYS;
+		goto end;
+	}
+
 	err = snd_card_new(&unit->device, index[card_index], id[card_index],
 			   THIS_MODULE, sizeof(struct snd_bebob), &card);
 	if (err < 0)
@@ -151,6 +158,7 @@ bebob_probe(struct fw_unit *unit,
 
 	bebob->card = card;
 	bebob->unit = unit;
+	bebob->spec = spec;
 	mutex_init(&bebob->mutex);
 	spin_lock_init(&bebob->lock);
 	init_waitqueue_head(&bebob->hwdep_wait);
@@ -216,62 +224,72 @@ static void bebob_remove(struct fw_unit *unit)
 	snd_card_free_when_closed(bebob->card);
 }
 
+struct snd_bebob_rate_spec normal_rate_spec = {
+	.get	= &snd_bebob_stream_get_rate,
+	.set	= &snd_bebob_stream_set_rate
+};
+static const struct snd_bebob_spec spec_normal = {
+	.clock	= NULL,
+	.rate	= &normal_rate_spec,
+	.meter	= NULL
+};
+
 static const struct ieee1394_device_id bebob_id_table[] = {
 	/* Edirol, FA-66 */
-	SND_BEBOB_DEV_ENTRY(VEN_EDIROL, 0x00010049),
+	SND_BEBOB_DEV_ENTRY(VEN_EDIROL, 0x00010049, &spec_normal),
 	/* Edirol, FA-101 */
-	SND_BEBOB_DEV_ENTRY(VEN_EDIROL, 0x00010048),
+	SND_BEBOB_DEV_ENTRY(VEN_EDIROL, 0x00010048, &spec_normal),
 	/* Presonus, FIREBOX */
-	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010000),
+	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010000, &spec_normal),
 	/* PreSonus, FIREPOD/FP10 */
-	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010066),
+	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010066, &spec_normal),
 	/* PreSonus, Inspire1394 */
-	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010001),
+	SND_BEBOB_DEV_ENTRY(VEN_PRESONUS, 0x00010001, &spec_normal),
 	/* BridgeCo, RDAudio1 */
-	SND_BEBOB_DEV_ENTRY(VEN_BRIDGECO, 0x00010048),
+	SND_BEBOB_DEV_ENTRY(VEN_BRIDGECO, 0x00010048, &spec_normal),
 	/* BridgeCo, Audio5 */
-	SND_BEBOB_DEV_ENTRY(VEN_BRIDGECO, 0x00010049),
+	SND_BEBOB_DEV_ENTRY(VEN_BRIDGECO, 0x00010049, &spec_normal),
 	/* Mackie, Onyx 1220/1620/1640 (Firewire I/O Card) */
-	SND_BEBOB_DEV_ENTRY(VEN_MACKIE, 0x00010065),
+	SND_BEBOB_DEV_ENTRY(VEN_MACKIE, 0x00010065, &spec_normal),
 	/* Mackie, d.2 (Firewire Option) */
-	SND_BEBOB_DEV_ENTRY(VEN_MACKIE, 0x00010067),
+	SND_BEBOB_DEV_ENTRY(VEN_MACKIE, 0x00010067, &spec_normal),
 	/* Stanton, ScratchAmp */
-	SND_BEBOB_DEV_ENTRY(VEN_STANTON, 0x00000001),
+	SND_BEBOB_DEV_ENTRY(VEN_STANTON, 0x00000001, &spec_normal),
 	/* Tascam, IF-FW DM */
-	SND_BEBOB_DEV_ENTRY(VEN_TASCAM, 0x00010067),
+	SND_BEBOB_DEV_ENTRY(VEN_TASCAM, 0x00010067, &spec_normal),
 	/* Behringer, XENIX UFX 1204 */
-	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00001204),
+	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00001204, &spec_normal),
 	/* Behringer, XENIX UFX 1604 */
-	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00001604),
+	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00001604, &spec_normal),
 	/* Behringer, Digital Mixer X32 series (X-UF Card) */
-	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00000006),
+	SND_BEBOB_DEV_ENTRY(VEN_BEHRINGER, 0x00000006, &spec_normal),
 	/* Apogee Electronics, Rosetta 200/400 (X-FireWire card) */
 	/* Apogee Electronics, DA/AD/DD-16X (X-FireWire card) */
-	SND_BEBOB_DEV_ENTRY(VEN_APOGEE, 0x00010048),
+	SND_BEBOB_DEV_ENTRY(VEN_APOGEE, 0x00010048, &spec_normal),
 	/* Apogee Electronics, Ensemble */
-	SND_BEBOB_DEV_ENTRY(VEN_APOGEE, 0x00001eee),
+	SND_BEBOB_DEV_ENTRY(VEN_APOGEE, 0x00001eee, &spec_normal),
 	/* ESI, Quatafire610 */
-	SND_BEBOB_DEV_ENTRY(VEN_ESI, 0x00010064),
+	SND_BEBOB_DEV_ENTRY(VEN_ESI, 0x00010064, &spec_normal),
 	/* AcousticReality, eARMasterOne */
-	SND_BEBOB_DEV_ENTRY(VEN_ACOUSTIC, 0x00000002),
+	SND_BEBOB_DEV_ENTRY(VEN_ACOUSTIC, 0x00000002, &spec_normal),
 	/* CME, MatrixKFW */
-	SND_BEBOB_DEV_ENTRY(VEN_CME, 0x00030000),
+	SND_BEBOB_DEV_ENTRY(VEN_CME, 0x00030000, &spec_normal),
 	/* Phonic, Helix Board 12 MkII */
-	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00050000),
+	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00050000, &spec_normal),
 	/* Phonic, Helix Board 18 MkII */
-	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00060000),
+	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00060000, &spec_normal),
 	/* Phonic, Helix Board 24 MkII */
-	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00070000),
+	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00070000, &spec_normal),
 	/* Phonic, Helix Board 12 Universal/18 Universal/24 Universal */
-	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00000000),
+	SND_BEBOB_DEV_ENTRY(VEN_PHONIC, 0x00000000, &spec_normal),
 	/* Lynx, Aurora 8/16 (LT-FW) */
-	SND_BEBOB_DEV_ENTRY(VEN_LYNX, 0x00000001),
+	SND_BEBOB_DEV_ENTRY(VEN_LYNX, 0x00000001, &spec_normal),
 	/* ICON, FireXon */
-	SND_BEBOB_DEV_ENTRY(VEN_ICON, 0x00000001),
+	SND_BEBOB_DEV_ENTRY(VEN_ICON, 0x00000001, &spec_normal),
 	/* PrismSound, Orpheus */
-	SND_BEBOB_DEV_ENTRY(VEN_PRISMSOUND, 0x00010048),
+	SND_BEBOB_DEV_ENTRY(VEN_PRISMSOUND, 0x00010048, &spec_normal),
 	/* PrismSound, ADA-8XR */
-	SND_BEBOB_DEV_ENTRY(VEN_PRISMSOUND, 0x0000ada8),
+	SND_BEBOB_DEV_ENTRY(VEN_PRISMSOUND, 0x0000ada8, &spec_normal),
 	/* IDs are unknown but able to be supported */
 	/*  Apogee, Mini-ME Firewire */
 	/*  Apogee, Mini-DAC Firewire */
diff --git a/sound/firewire/bebob/bebob.h b/sound/firewire/bebob/bebob.h
index e8a5e44..7365f92 100644
--- a/sound/firewire/bebob/bebob.h
+++ b/sound/firewire/bebob/bebob.h
@@ -48,6 +48,28 @@ struct snd_bebob_stream_formation {
 /* this is a lookup table for index of stream formations */
 extern const unsigned int snd_bebob_rate_table[SND_BEBOB_STRM_FMT_ENTRIES];
 
+/* device specific operations */
+#define SND_BEBOB_CLOCK_INTERNAL	"Internal"
+struct snd_bebob_clock_spec {
+	unsigned int num;
+	char *const *labels;
+	int (*get)(struct snd_bebob *bebob, unsigned int *id);
+};
+struct snd_bebob_rate_spec {
+	int (*get)(struct snd_bebob *bebob, unsigned int *rate);
+	int (*set)(struct snd_bebob *bebob, unsigned int rate);
+};
+struct snd_bebob_meter_spec {
+	unsigned int num;
+	char *const *labels;
+	int (*get)(struct snd_bebob *bebob, u32 *target, unsigned int size);
+};
+struct snd_bebob_spec {
+	struct snd_bebob_clock_spec *clock;
+	struct snd_bebob_rate_spec *rate;
+	struct snd_bebob_meter_spec *meter;
+};
+
 struct snd_bebob {
 	struct snd_card *card;
 	struct fw_unit *unit;
@@ -56,6 +78,8 @@ struct snd_bebob {
 	struct mutex mutex;
 	spinlock_t lock;
 
+	const struct snd_bebob_spec *spec;
+
 	unsigned int midi_input_ports;
 	unsigned int midi_output_ports;
 
@@ -100,6 +124,12 @@ snd_bebob_read_quad(struct fw_unit *unit, u64 addr, u32 *buf)
 				  (void *)buf, sizeof(u32), 0);
 }
 
+/* AV/C Audio Subunit Specification 1.0 (Oct 2000, 1394TA) */
+int avc_audio_set_selector(struct fw_unit *unit, unsigned int subunit_id,
+			   unsigned int fb_id, unsigned int num);
+int avc_audio_get_selector(struct fw_unit *unit, unsigned  int subunit_id,
+			   unsigned int fb_id, unsigned int *num);
+
 /*
  * AVC command extensions, AV/C Unit and Subunit, Revision 17
  * (Nov 2003, BridgeCo)
@@ -194,12 +224,13 @@ int snd_bebob_create_pcm_devices(struct snd_bebob *bebob);
 
 int snd_bebob_create_hwdep_device(struct snd_bebob *bebob);
 
-#define SND_BEBOB_DEV_ENTRY(vendor, model) \
+#define SND_BEBOB_DEV_ENTRY(vendor, model, data) \
 { \
 	.match_flags	= IEEE1394_MATCH_VENDOR_ID | \
 			  IEEE1394_MATCH_MODEL_ID, \
 	.vendor_id	= vendor, \
 	.model_id	= model, \
+	.driver_data	= (kernel_ulong_t)data \
 }
 
 #endif
diff --git a/sound/firewire/bebob/bebob_command.c b/sound/firewire/bebob/bebob_command.c
index 6a01795..9402cc1 100644
--- a/sound/firewire/bebob/bebob_command.c
+++ b/sound/firewire/bebob/bebob_command.c
@@ -8,6 +8,83 @@
 
 #include "./bebob.h"
 
+int avc_audio_set_selector(struct fw_unit *unit, unsigned int subunit_id,
+			   unsigned int fb_id, unsigned int num)
+{
+	u8 *buf;
+	int err;
+
+	buf = kzalloc(12, GFP_KERNEL);
+	if (buf == NULL)
+		return -ENOMEM;
+
+	buf[0]  = 0x00;		/* AV/C CONTROL */
+	buf[1]  = 0x08 | (0x07 & subunit_id);	/* AUDIO SUBUNIT ID */
+	buf[2]  = 0xb8;		/* FUNCTION BLOCK  */
+	buf[3]  = 0x80;		/* type is 'selector'*/
+	buf[4]  = 0xff & fb_id;	/* function block id */
+	buf[5]  = 0x10;		/* control attribute is CURRENT */
+	buf[6]  = 0x02;		/* selector length is 2 */
+	buf[7]  = 0xff & num;	/* input function block plug number */
+	buf[8]  = 0x01;		/* control selector is SELECTOR_CONTROL */
+
+	err = fcp_avc_transaction(unit, buf, 12, buf, 12,
+				  BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5) |
+				  BIT(6) | BIT(7) | BIT(8));
+	if (err > 0 && err < 9)
+		err = -EIO;
+	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
+		err = -ENOSYS;
+	else if (buf[0] == 0x0a) /* REJECTED */
+		err = -EINVAL;
+	else if (err > 0)
+		err = 0;
+
+	kfree(buf);
+	return err;
+}
+
+int avc_audio_get_selector(struct fw_unit *unit, unsigned int subunit_id,
+			   unsigned int fb_id, unsigned int *num)
+{
+	u8 *buf;
+	int err;
+
+	buf = kzalloc(12, GFP_KERNEL);
+	if (buf == NULL)
+		return -ENOMEM;
+
+	buf[0]  = 0x01;		/* AV/C STATUS */
+	buf[1]  = 0x08 | (0x07 & subunit_id);	/* AUDIO SUBUNIT ID */
+	buf[2]  = 0xb8;		/* FUNCTION BLOCK */
+	buf[3]  = 0x80;		/* type is 'selector'*/
+	buf[4]  = 0xff & fb_id;	/* function block id */
+	buf[5]  = 0x10;		/* control attribute is CURRENT */
+	buf[6]  = 0x02;		/* selector length is 2 */
+	buf[7]  = 0xff;		/* input function block plug number */
+	buf[8]  = 0x01;		/* control selector is SELECTOR_CONTROL */
+
+	err = fcp_avc_transaction(unit, buf, 12, buf, 12,
+				  BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5) |
+				  BIT(6) | BIT(8));
+	if (err > 0 && err < 9)
+		err = -EIO;
+	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
+		err = -ENOSYS;
+	else if (buf[0] == 0x0a) /* REJECTED */
+		err = -EINVAL;
+	else if (buf[0] == 0x0b) /* IN TRANSITION */
+		err = -EAGAIN;
+	if (err < 0)
+		goto end;
+
+	*num = buf[7];
+	err = 0;
+end:
+	kfree(buf);
+	return err;
+}
+
 static inline void
 avc_bridgeco_fill_extension_addr(u8 *buf, u8 *addr)
 {
diff --git a/sound/firewire/bebob/bebob_pcm.c b/sound/firewire/bebob/bebob_pcm.c
index 9d86817..4a55561 100644
--- a/sound/firewire/bebob/bebob_pcm.c
+++ b/sound/firewire/bebob/bebob_pcm.c
@@ -155,6 +155,7 @@ static int
 pcm_open(struct snd_pcm_substream *substream)
 {
 	struct snd_bebob *bebob = substream->private_data;
+	struct snd_bebob_rate_spec *spec = bebob->spec->rate;
 	unsigned int sampling_rate;
 	bool internal;
 	int err;
@@ -178,7 +179,7 @@ pcm_open(struct snd_pcm_substream *substream)
 	if (!internal ||
 	    amdtp_stream_pcm_running(&bebob->tx_stream) ||
 	    amdtp_stream_pcm_running(&bebob->rx_stream)) {
-		err = snd_bebob_stream_get_rate(bebob, &sampling_rate);
+		err = spec->get(bebob, &sampling_rate);
 		if (err < 0) {
 			dev_err(&bebob->unit->device,
 				"fail to get sampling rate: %d\n", err);
diff --git a/sound/firewire/bebob/bebob_proc.c b/sound/firewire/bebob/bebob_proc.c
index c31ca4f..335da64 100644
--- a/sound/firewire/bebob/bebob_proc.c
+++ b/sound/firewire/bebob/bebob_proc.c
@@ -69,6 +69,39 @@ end:
 }
 
 static void
+proc_read_meters(struct snd_info_entry *entry,
+		 struct snd_info_buffer *buffer)
+{
+	struct snd_bebob *bebob = entry->private_data;
+	struct snd_bebob_meter_spec *spec = bebob->spec->meter;
+	u32 *buf;
+	unsigned int i, c, channels, size;
+
+	if (spec == NULL)
+		return;
+
+	channels = spec->num * 2;
+	size = channels * sizeof(u32);
+	buf = kmalloc(size, GFP_KERNEL);
+	if (buf == NULL)
+		return;
+
+	if (spec->get(bebob, buf, size) < 0)
+		goto end;
+
+	for (i = 0, c = 1; i < channels; i++) {
+		snd_iprintf(buffer, "%s %d:\t%d\n",
+			    spec->labels[i / 2], c++, buf[i]);
+		if ((i + 1 < channels - 1) &&
+		    (strcmp(spec->labels[i / 2],
+			    spec->labels[(i + 1) / 2]) != 0))
+			c = 1;
+	}
+end:
+	kfree(buf);
+}
+
+static void
 proc_read_formation(struct snd_info_entry *entry,
 		struct snd_info_buffer *buffer)
 {
@@ -100,16 +133,25 @@ proc_read_clock(struct snd_info_entry *entry,
 		struct snd_info_buffer *buffer)
 {
 	struct snd_bebob *bebob = entry->private_data;
-	unsigned int rate;
+	struct snd_bebob_rate_spec *rate_spec = bebob->spec->rate;
+	struct snd_bebob_clock_spec *clk_spec = bebob->spec->clock;
+	unsigned int rate, id;
 	bool internal;
 
-	if (snd_bebob_stream_get_rate(bebob, &rate) >= 0)
+	if (rate_spec->get(bebob, &rate) >= 0)
 		snd_iprintf(buffer, "Sampling rate: %d\n", rate);
 
-	if (snd_bebob_stream_check_internal_clock(bebob, &internal) >= 0)
-		snd_iprintf(buffer, "Clock Source: %s (MSU-dest: %d)",
-			    (internal) ? "Internal" : "External",
-			    bebob->sync_input_plug);
+	if (clk_spec) {
+		if (clk_spec->get(bebob, &id) >= 0)
+			snd_iprintf(buffer, "Clock Source: %s\n",
+				    clk_spec->labels[id]);
+	} else {
+		if (snd_bebob_stream_check_internal_clock(bebob,
+							  &internal) >= 0)
+			snd_iprintf(buffer, "Clock Source: %s (MSU-dest: %d)\n",
+				    (internal) ? "Internal" : "External",
+				    bebob->sync_input_plug);
+	}
 }
 
 static void
@@ -148,4 +190,7 @@ void snd_bebob_proc_init(struct snd_bebob *bebob)
 	add_node(bebob, root, "clock", proc_read_clock);
 	add_node(bebob, root, "firmware", proc_read_hw_info);
 	add_node(bebob, root, "formation", proc_read_formation);
+
+	if (bebob->spec->meter != NULL)
+		add_node(bebob, root, "meter", proc_read_meters);
 }
diff --git a/sound/firewire/bebob/bebob_stream.c b/sound/firewire/bebob/bebob_stream.c
index 85b4fd6..4a21dcf 100644
--- a/sound/firewire/bebob/bebob_stream.c
+++ b/sound/firewire/bebob/bebob_stream.c
@@ -119,13 +119,27 @@ end:
 int
 snd_bebob_stream_check_internal_clock(struct snd_bebob *bebob, bool *internal)
 {
+	struct snd_bebob_clock_spec *clk_spec = bebob->spec->clock;
 	u8 addr[AVC_BRIDGECO_ADDR_BYTES], input[7];
+	unsigned int id;
 	int err = 0;
 
 	*internal = false;
 
+	/* 1.The device has its own operation to switch source of clock */
+	if (clk_spec) {
+		err = clk_spec->get(bebob, &id);
+		if (err < 0)
+			dev_err(&bebob->unit->device,
+				"fail to get clock source: %d\n", err);
+		else if (strncmp(clk_spec->labels[id], SND_BEBOB_CLOCK_INTERNAL,
+				 strlen(SND_BEBOB_CLOCK_INTERNAL)) == 0)
+			*internal = true;
+		goto end;
+	}
+
 	/*
-	 * 1.The device don't support to switch source of clock then assumed
+	 * 2.The device don't support to switch source of clock then assumed
 	 *   to use internal clock always
 	 */
 	if (bebob->sync_input_plug < 0) {
@@ -134,7 +148,7 @@ snd_bebob_stream_check_internal_clock(struct snd_bebob *bebob, bool *internal)
 	}
 
 	/*
-	 * 2.The device supports to switch source of clock by an usual way.
+	 * 3.The device supports to switch source of clock by an usual way.
 	 *   Let's check input for 'Music Sub Unit Sync Input' plug.
 	 */
 	avc_bridgeco_fill_msu_addr(addr, AVC_BRIDGECO_PLUG_DIR_IN,
@@ -442,6 +456,7 @@ end:
 
 int snd_bebob_stream_start_duplex(struct snd_bebob *bebob, int rate)
 {
+	struct snd_bebob_rate_spec *rate_spec = bebob->spec->rate;
 	struct amdtp_stream *master, *slave;
 	atomic_t *slave_substreams;
 	enum cip_flags sync_mode;
@@ -508,7 +523,7 @@ int snd_bebob_stream_start_duplex(struct snd_bebob *bebob, int rate)
 		break_both_connections(bebob);
 
 	/* stop streams if rate is different */
-	err = snd_bebob_stream_get_rate(bebob, &curr_rate);
+	err = rate_spec->get(bebob, &curr_rate);
 	if (err < 0) {
 		dev_err(&bebob->unit->device,
 			"fail to get sampling rate: %d\n", err);
@@ -532,7 +547,7 @@ int snd_bebob_stream_start_duplex(struct snd_bebob *bebob, int rate)
 		 * If establishing connections at first, Yamaha GO46
 		 * (and maybe Terratec X24) don't generate sound.
 		 */
-		err = snd_bebob_stream_set_rate(bebob, rate);
+		err = rate_spec->set(bebob, rate);
 		if (err < 0) {
 			dev_err(&bebob->unit->device,
 				"fail to set sampling rate: %d\n",
@@ -822,6 +837,7 @@ end:
 
 int snd_bebob_stream_discover(struct snd_bebob *bebob)
 {
+	struct snd_bebob_clock_spec *clk_spec = bebob->spec->clock;
 	u8 plugs[AVC_PLUG_INFO_BUF_BYTES], addr[AVC_BRIDGECO_ADDR_BYTES];
 	enum avc_bridgeco_plug_type type;
 	unsigned int i;
@@ -908,7 +924,8 @@ int snd_bebob_stream_discover(struct snd_bebob *bebob)
 	}
 
 	/* for check source of clock later */
-	err = seek_msu_sync_input_plug(bebob);
+	if (!clk_spec)
+		err = seek_msu_sync_input_plug(bebob);
 end:
 	return err;
 }