Commit 8fe9a03f authored by Pavel Hofman's avatar Pavel Hofman Committed by Greg Kroah-Hartman
Browse files

usb: gadget: u_audio: Rate ctl notifies about current srate (0=stopped) 

The Playback/Capture ctl currently reports rate value set by USB
control selector UAC2_CS_CONTROL_SAM_FREQ (fixed for UAC1). When the
stops playback/capture, the reported value does not change.  The gadget
side has no information whether the host has started/stopped
capture/playback.

This patch sets the value reported by the respective rate ctl to zero
when the host side has stopped playback/capture. Also, it calls
snd_ctl_notify when start/stop  occurs, so that a subscribed client can
act appropriately.

Tests have confirmed that USB hosts change UAC2_CS_CONTROL_SAM_FREQ
before switching altsetting to activate playback/capture, resulting in
correct order (params->c/p_srate is set to requested rate before
u_audio_start_capture/playback is called).

The gadget rate notifications are used by user-space audio gadget
controller gaudio_ctl https://github.com/pavhofman/gaudio_ctl

.

Signed-off-by: default avatarPavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20220121155308.48794-8-pavel.hofman@ivitera.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 695d39ff

drivers/usb/gadget/function/u_audio.c

+27 −1
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ struct uac_rtd_params { 


	struct snd_kcontrol *snd_kctl_rate; /* read-only current rate */

	int srate; /* selected samplerate */

	int active; /* playback/capture running */



  spinlock_t lock; /* lock for control transfers */
@@ -490,6 +491,21 @@ static inline void free_ep_fback(struct uac_rtd_params *prm, struct usb_ep *ep) 
		dev_err(uac->card->dev, "%s:%d Error!\n", __func__, __LINE__);

}



static void set_active(struct uac_rtd_params *prm, bool active)

{

	// notifying through the Rate ctrl

	struct snd_kcontrol *kctl = prm->snd_kctl_rate;

	unsigned long flags;



	spin_lock_irqsave(&prm->lock, flags);

	if (prm->active != active) {

		prm->active = active;

		snd_ctl_notify(prm->uac->card, SNDRV_CTL_EVENT_MASK_VALUE,

				&kctl->id);

	}

	spin_unlock_irqrestore(&prm->lock, flags);

}



int u_audio_set_capture_srate(struct g_audio *audio_dev, int srate)

{

	struct uac_params *params = &audio_dev->params;
@@ -607,6 +623,8 @@ int u_audio_start_capture(struct g_audio *audio_dev) 
			dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);

	}



	set_active(&uac->c_prm, true);



	ep_fback = audio_dev->in_ep_fback;

	if (!ep_fback)

		return 0;
@@ -652,6 +670,7 @@ void u_audio_stop_capture(struct g_audio *audio_dev) 
{

	struct snd_uac_chip *uac = audio_dev->uac;



	set_active(&uac->c_prm, false);

	if (audio_dev->in_ep_fback)

		free_ep_fback(&uac->c_prm, audio_dev->in_ep_fback);

	free_ep(&uac->c_prm, audio_dev->out_ep);
@@ -723,6 +742,8 @@ int u_audio_start_playback(struct g_audio *audio_dev) 
			dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);

	}



	set_active(&uac->p_prm, true);



	return 0;

}

EXPORT_SYMBOL_GPL(u_audio_start_playback);
@@ -731,6 +752,7 @@ void u_audio_stop_playback(struct g_audio *audio_dev) 
{

	struct snd_uac_chip *uac = audio_dev->uac;



	set_active(&uac->p_prm, false);

	free_ep(&uac->p_prm, audio_dev->in_ep);

}

EXPORT_SYMBOL_GPL(u_audio_stop_playback);
@@ -1074,7 +1096,11 @@ static int u_audio_rate_get(struct snd_kcontrol *kcontrol, 
	unsigned long flags;



	spin_lock_irqsave(&prm->lock, flags);

	if (prm->active)

		ucontrol->value.integer.value[0] = prm->srate;

	else

		/* not active: reporting zero rate */

		ucontrol->value.integer.value[0] = 0;

	spin_unlock_irqrestore(&prm->lock, flags);

	return 0;

}