ANDROID: sound: usb: Add helper APIs to enable audio stream

Adding helper API to find usb substream context information
using card number, pcm device number and direction. This usb
substream is used to enable/disable by issuing SET_ALT
command to device. Also add disconnect call back to perform
any clean up required.

Bug: 140989596
Change-Id: I252f5171bd94b5ab096eb1a2f053f29a8c049c3b
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>

sound/usb/card.c

@@ -106,6 +106,72 @@ static DEFINE_MUTEX(register_mutex);
 static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
 static struct usb_driver usb_audio_driver;
 
+struct snd_usb_substream *find_snd_usb_substream(unsigned int card_num,
+	unsigned int pcm_idx, unsigned int direction, struct snd_usb_audio
+	**uchip, void (*disconnect_cb)(struct snd_usb_audio *chip))
+{
+	int idx;
+	struct snd_usb_stream *as;
+	struct snd_usb_substream *subs = NULL;
+	struct snd_usb_audio *chip = NULL;
+
+	mutex_lock(&register_mutex);
+	/*
+	 * legacy audio snd card number assignment is dynamic. Hence
+	 * search using chip->card->number
+	 */
+	for (idx = 0; idx < SNDRV_CARDS; idx++) {
+		if (!usb_chip[idx])
+			continue;
+		if (usb_chip[idx]->card->number == card_num) {
+			chip = usb_chip[idx];
+			break;
+		}
+	}
+
+	if (!chip || atomic_read(&chip->shutdown)) {
+		pr_debug("%s: instance of usb crad # %d does not exist\n",
+			__func__, card_num);
+		goto err;
+	}
+
+	if (pcm_idx >= chip->pcm_devs) {
+		pr_err("%s: invalid pcm dev number %u > %d\n", __func__,
+			pcm_idx, chip->pcm_devs);
+		goto err;
+	}
+
+	if (direction > SNDRV_PCM_STREAM_CAPTURE) {
+		pr_err("%s: invalid direction %u\n", __func__, direction);
+		goto err;
+	}
+
+	list_for_each_entry(as, &chip->pcm_list, list) {
+		if (as->pcm_index == pcm_idx) {
+			subs = &as->substream[direction];
+			if (subs->interface < 0 && !subs->data_endpoint &&
+				!subs->sync_endpoint) {
+				pr_debug("%s: stream disconnected, bail out\n",
+					__func__);
+				subs = NULL;
+				goto err;
+			}
+			goto done;
+		}
+	}
+
+done:
+	chip->card_num = card_num;
+	chip->disconnect_cb = disconnect_cb;
+err:
+	*uchip = chip;
+	if (!subs)
+		pr_debug("%s: substream instance not found\n", __func__);
+	mutex_unlock(&register_mutex);
+	return subs;
+}
+EXPORT_SYMBOL_GPL(find_snd_usb_substream);
+
 /*
  * disconnect streams
  * called from usb_audio_disconnect()
@@ -341,6 +407,7 @@ static void snd_usb_audio_free(struct snd_card *card)
 	list_for_each_entry_safe(ep, n, &chip->ep_list, list)
 		snd_usb_endpoint_free(ep);
 
+	mutex_destroy(&chip->dev_lock);
 	mutex_destroy(&chip->mutex);
 	if (!atomic_read(&chip->shutdown))
 		dev_set_drvdata(&chip->dev->dev, NULL);
@@ -468,6 +535,7 @@ static int snd_usb_audio_create(struct usb_interface *intf,
 
 	chip = card->private_data;
 	mutex_init(&chip->mutex);
+	mutex_init(&chip->dev_lock);
 	init_waitqueue_head(&chip->shutdown_wait);
 	chip->index = idx;
 	chip->dev = dev;
@@ -700,6 +768,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 
 	card = chip->card;
 
+	if (chip->disconnect_cb)
+		chip->disconnect_cb(chip);
+
 	mutex_lock(&register_mutex);
 	if (atomic_inc_return(&chip->shutdown) == 1) {
 		struct snd_usb_stream *as;

sound/usb/card.h

@@ -175,4 +175,8 @@ struct snd_usb_stream {
 	struct list_head list;
 };
 
+struct snd_usb_substream *find_snd_usb_substream(unsigned int card_num,
+	unsigned int pcm_idx, unsigned int direction, struct snd_usb_audio
+	**uchip, void (*disconnect_cb)(struct snd_usb_audio *chip));
+
 #endif /* __USBAUDIO_CARD_H */

sound/usb/pcm.c

@@ -138,6 +138,69 @@ static struct audioformat *find_format(struct snd_usb_substream *subs)
 	return found;
 }
 
+/*
+ * find a matching audio format as well as non-zero service interval
+ */
+static struct audioformat *find_format_and_si(struct snd_usb_substream *subs,
+	unsigned int datainterval)
+{
+	unsigned int i;
+	struct audioformat *fp;
+	struct audioformat *found = NULL;
+	int cur_attr = 0, attr;
+
+	list_for_each_entry(fp, &subs->fmt_list, list) {
+		if (datainterval != fp->datainterval)
+			continue;
+		if (!(fp->formats & pcm_format_to_bits(subs->pcm_format)))
+			continue;
+		if (fp->channels != subs->channels)
+			continue;
+		if (subs->cur_rate < fp->rate_min ||
+		    subs->cur_rate > fp->rate_max)
+			continue;
+		if (!(fp->rates & SNDRV_PCM_RATE_CONTINUOUS)) {
+			for (i = 0; i < fp->nr_rates; i++)
+				if (fp->rate_table[i] == subs->cur_rate)
+					break;
+			if (i >= fp->nr_rates)
+				continue;
+		}
+		attr = fp->ep_attr & USB_ENDPOINT_SYNCTYPE;
+		if (!found) {
+			found = fp;
+			cur_attr = attr;
+			continue;
+		}
+		/* avoid async out and adaptive in if the other method
+		 * supports the same format.
+		 * this is a workaround for the case like
+		 * M-audio audiophile USB.
+		 */
+		if (attr != cur_attr) {
+			if ((attr == USB_ENDPOINT_SYNC_ASYNC &&
+			     subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
+			    (attr == USB_ENDPOINT_SYNC_ADAPTIVE &&
+			     subs->direction == SNDRV_PCM_STREAM_CAPTURE))
+				continue;
+			if ((cur_attr == USB_ENDPOINT_SYNC_ASYNC &&
+			     subs->direction == SNDRV_PCM_STREAM_PLAYBACK) ||
+			    (cur_attr == USB_ENDPOINT_SYNC_ADAPTIVE &&
+			     subs->direction == SNDRV_PCM_STREAM_CAPTURE)) {
+				found = fp;
+				cur_attr = attr;
+				continue;
+			}
+		}
+		/* find the format with the largest max. packet size */
+		if (fp->maxpacksize > found->maxpacksize) {
+			found = fp;
+			cur_attr = attr;
+		}
+	}
+	return found;
+}
+
 static int init_pitch_v1(struct snd_usb_audio *chip, int iface,
 			 struct usb_host_interface *alts,
 			 struct audioformat *fmt)
@@ -570,6 +633,74 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 	return 0;
 }
 
+int snd_usb_enable_audio_stream(struct snd_usb_substream *subs,
+	int datainterval, bool enable)
+{
+	struct audioformat *fmt;
+	struct usb_host_interface *alts;
+	struct usb_interface *iface;
+	int ret;
+
+	if (!enable) {
+		if (subs->interface >= 0) {
+			usb_set_interface(subs->dev, subs->interface, 0);
+			subs->altset_idx = 0;
+			subs->interface = -1;
+			subs->cur_audiofmt = NULL;
+		}
+
+		snd_usb_autosuspend(subs->stream->chip);
+		return 0;
+	}
+
+	snd_usb_autoresume(subs->stream->chip);
+	if (datainterval != -EINVAL)
+		fmt = find_format_and_si(subs, datainterval);
+	else
+		fmt = find_format(subs);
+	if (!fmt) {
+		dev_err(&subs->dev->dev,
+		"cannot set format: format = %#x, rate = %d, channels = %d\n",
+			   subs->pcm_format, subs->cur_rate, subs->channels);
+		return -EINVAL;
+	}
+
+	subs->altset_idx = 0;
+	subs->interface = -1;
+	if (atomic_read(&subs->stream->chip->shutdown)) {
+		ret = -ENODEV;
+	} else {
+		ret = set_format(subs, fmt);
+		if (ret < 0)
+			return ret;
+
+		iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
+		if (!iface) {
+			dev_err(&subs->dev->dev, "Could not get iface %d\n",
+				subs->cur_audiofmt->iface);
+			return -ENODEV;
+		}
+
+		alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
+		ret = snd_usb_init_sample_rate(subs->stream->chip,
+					       subs->cur_audiofmt->iface,
+					       alts,
+					       subs->cur_audiofmt,
+					       subs->cur_rate);
+		if (ret < 0) {
+			dev_err(&subs->dev->dev, "failed to set rate %d\n",
+				subs->cur_rate);
+			return ret;
+		}
+	}
+
+	subs->interface = fmt->iface;
+	subs->altset_idx = fmt->altset_idx;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_enable_audio_stream);
+
 /*
  * Return the score of matching two audioformats.
  * Veto the audioformat if:

sound/usb/pcm.h

@@ -14,5 +14,7 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
 		       struct audioformat *fmt);
 void snd_usb_preallocate_buffer(struct snd_usb_substream *subs);
 
+int snd_usb_enable_audio_stream(struct snd_usb_substream *subs,
+				int datainterval, bool enable);
 
 #endif /* __USBAUDIO_PCM_H */

sound/usb/stream.c

@@ -67,9 +67,13 @@ static void snd_usb_audio_stream_free(struct snd_usb_stream *stream)
 static void snd_usb_audio_pcm_free(struct snd_pcm *pcm)
 {
 	struct snd_usb_stream *stream = pcm->private_data;
+	struct snd_usb_audio *chip;
 	if (stream) {
+		mutex_lock(&stream->chip->dev_lock);
+		chip = stream->chip;
 		stream->pcm = NULL;
 		snd_usb_audio_stream_free(stream);
+		mutex_unlock(&chip->dev_lock);
 	}
 }
 

sound/usb/usbaudio.h

@@ -57,6 +57,9 @@ struct snd_usb_audio {
 	struct usb_host_interface *ctrl_intf;	/* the audio control interface */
 	struct media_device *media_dev;
 	struct media_intf_devnode *ctl_intf_media_devnode;
+	struct mutex dev_lock;  /* to protect any race with disconnect */
+	int card_num;	/* cache pcm card number to use upon disconnect */
+	void (*disconnect_cb)(struct snd_usb_audio *chip);
 };
 
 #define usb_audio_err(chip, fmt, args...) \