[PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[JaeHun Jung]

In mobile, a co-processor is used when using USB audio
to improve power consumption.
hooking is required for sync-up when operating
the co-processor. So register call-back function.
The main operation of the call-back function is as follows:
- Initialize the co-processor by transmitting data
  when initializing.
- Change the co-processor setting value through
  the interface function.
- Configure sampling rate
- pcm open/close

Bug: 156315379

Change-Id: I32e1dd408e64aaef68ee06c480c4b4d4c95546dc
Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
---
 sound/usb/card.c     | 16 ++++++++++++++++
 sound/usb/card.h     |  1 +
 sound/usb/clock.c    |  5 +++++
 sound/usb/pcm.c      | 33 +++++++++++++++++++++++++++++++++
 sound/usb/usbaudio.h | 30 ++++++++++++++++++++++++++++++
 5 files changed, 85 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index fd6fd17..2f3fa14 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -111,6 +111,7 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
 static DEFINE_MUTEX(register_mutex);
 static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
 static struct usb_driver usb_audio_driver;
+struct snd_usb_audio_vendor_ops *usb_audio_ops;
 
 /*
  * disconnect streams
@@ -210,6 +211,12 @@ static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int int
 	return 0;
 }
 
+void snd_set_vender_interface(struct snd_usb_audio_vendor_ops *vendor_ops)
+{
+	usb_audio_ops = vendor_ops;
+}
+EXPORT_SYMBOL_GPL(snd_set_vender_interface);
+
 /*
  * parse audio control descriptor and create pcm/midi streams
  */
@@ -598,6 +605,9 @@ static int usb_audio_probe(struct usb_interface *intf,
 	if (err < 0)
 		return err;
 
+	if (usb_audio_ops && usb_audio_ops->vendor_conn)
+		usb_audio_ops->vendor_conn(intf, dev);
+
 	/*
 	 * found a config.  now register to ALSA
 	 */
@@ -653,6 +663,9 @@ static int usb_audio_probe(struct usb_interface *intf,
 	}
 	dev_set_drvdata(&dev->dev, chip);
 
+	if (usb_audio_ops && usb_audio_ops->vendor_usb_add_ctls)
+		usb_audio_ops->vendor_usb_add_ctls(chip, 0);
+
 	/*
 	 * For devices with more than one control interface, we assume the
 	 * first contains the audio controls. We might need a more specific
@@ -737,6 +750,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 
 	card = chip->card;
 
+	if (usb_audio_ops && usb_audio_ops->vendor_disc)
+		usb_audio_ops->vendor_disc();
+
 	mutex_lock(&register_mutex);
 	if (atomic_inc_return(&chip->shutdown) == 1) {
 		struct snd_usb_stream *as;
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 395403a..a55bb4c 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -175,5 +175,6 @@ struct snd_usb_stream {
 	struct snd_usb_substream substream[2];
 	struct list_head list;
 };
+void snd_set_vender_interface(struct snd_usb_audio_vendor_ops *vendor_ops);
 
 #endif /* __USBAUDIO_CARD_H */
diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index b118cf9..0ceeccb 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -642,8 +642,13 @@ static int set_sample_rate_v2v3(struct snd_usb_audio *chip, int iface,
 	 * interface is active. */
 	if (rate != prev_rate) {
 		usb_set_interface(dev, iface, 0);
+		if (usb_audio_ops && usb_audio_ops->vendor_set_intf)
+			usb_audio_ops->vendor_set_intf(dev, alts, iface, 0);
 		snd_usb_set_interface_quirk(dev);
 		usb_set_interface(dev, iface, fmt->altsetting);
+		if (usb_audio_ops && usb_audio_ops->vendor_set_intf)
+			usb_audio_ops->vendor_set_intf(dev, alts, iface,
+					fmt->altsetting);
 		snd_usb_set_interface_quirk(dev);
 	}
 
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index a4e4064..6cdacac 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -134,6 +134,9 @@ static struct audioformat *find_format(struct snd_usb_substream *subs)
 			found = fp;
 			cur_attr = attr;
 		}
+
+		if (usb_audio_ops && usb_audio_ops->vendor_pcm_binterval)
+			usb_audio_ops->vendor_pcm_binterval(fp, found, &cur_attr, &attr);
 	}
 	return found;
 }
@@ -568,6 +571,9 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 		}
 		dev_dbg(&dev->dev, "setting usb interface %d:%d\n",
 			fmt->iface, fmt->altsetting);
+		if (usb_audio_ops && usb_audio_ops->vendor_set_pcm_intf)
+			usb_audio_ops->vendor_set_pcm_intf(dev, fmt->iface,
+					fmt->altsetting, subs->direction);
 		snd_usb_set_interface_quirk(dev);
 	}
 
@@ -891,6 +897,15 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	struct usb_interface *iface;
 	int ret;
 
+	if (usb_audio_ops && usb_audio_ops->vendor_set_pcmbuf) {
+		ret = usb_audio_ops->vendor_set_pcmbuf(subs->dev);
+
+		if (ret < 0) {
+			dev_err(&subs->dev->dev, "pcm buf transfer failed\n");
+			return ret;
+		}
+	}
+
 	if (! subs->cur_audiofmt) {
 		dev_err(&subs->dev->dev, "no format is specified!\n");
 		return -ENXIO;
@@ -924,6 +939,15 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 		if (ret < 0)
 			goto unlock;
 
+		if (usb_audio_ops && usb_audio_ops->vendor_set_rate) {
+			subs->need_setup_ep = false;
+			usb_audio_ops->vendor_set_rate(
+					subs->cur_audiofmt->iface,
+					subs->cur_rate,
+					subs->cur_audiofmt->altsetting);
+			goto unlock;
+		}
+
 		ret = configure_endpoint(subs);
 		if (ret < 0)
 			goto unlock;
@@ -1333,6 +1357,9 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream)
 	struct snd_usb_substream *subs = &as->substream[direction];
 	int ret;
 
+	if (usb_audio_ops && usb_audio_ops->vendor_pcm_con)
+		usb_audio_ops->vendor_pcm_con(true, direction);
+
 	subs->interface = -1;
 	subs->altset_idx = 0;
 	runtime->hw = snd_usb_hardware;
@@ -1361,12 +1388,18 @@ static int snd_usb_pcm_close(struct snd_pcm_substream *substream)
 	struct snd_usb_substream *subs = &as->substream[direction];
 	int ret;
 
+	if (usb_audio_ops && usb_audio_ops->vendor_pcm_con)
+		usb_audio_ops->vendor_pcm_con(false, direction);
+
 	snd_media_stop_pipeline(subs);
 
 	if (!as->chip->keep_iface &&
 	    subs->interface >= 0 &&
 	    !snd_usb_lock_shutdown(subs->stream->chip)) {
 		usb_set_interface(subs->dev, subs->interface, 0);
+		if (usb_audio_ops && usb_audio_ops->vendor_set_pcm_intf)
+			usb_audio_ops->vendor_set_pcm_intf(subs->dev,
+					subs->interface, 0, direction);
 		subs->interface = -1;
 		ret = snd_usb_pcm_change_state(subs, UAC3_PD_STATE_D1);
 		snd_usb_unlock_shutdown(subs->stream->chip);
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 1c892c7..a2fd8a4 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -124,4 +124,34 @@ void snd_usb_unlock_shutdown(struct snd_usb_audio *chip);
 extern bool snd_usb_use_vmalloc;
 extern bool snd_usb_skip_validation;
 
+/* for vender function mapping */
+extern struct snd_usb_audio_vendor_ops *usb_audio_ops;
+
+/* USB audio interface function for audio core */
+struct snd_usb_audio_vendor_ops {
+	/* Set descriptors and memory map */
+	void (*vendor_conn)(struct usb_interface *intf,
+			struct usb_device *udev);
+	/* Set disconnection */
+	void (*vendor_disc)(void);
+	/* Set interface info and setting value */
+	int (*vendor_set_intf)(struct usb_device *udev,
+			struct usb_host_interface *alts, int iface, int alt);
+	/* Set sample rate */
+	int (*vendor_set_rate)(int iface, int rate, int alt);
+	/* Alloc pcm buffer */
+	int (*vendor_set_pcmbuf)(struct usb_device *udev);
+	/* Set pcm interface */
+	int (*vendor_set_pcm_intf)(struct usb_device *udev,
+			int iface, int alt, int direction);
+	/* informed whether pcm open/close to vendor */
+	void (*vendor_pcm_con)(int onoff, int direction);
+	/* set datainterval */
+	void (*vendor_pcm_binterval)(void *fp, void *found,
+			int *cur_attr, int *attr);
+	/* control USB F/W */
+	int (*vendor_usb_add_ctls)(struct snd_usb_audio *chip,
+				unsigned long private_value);
+};
+
 #endif /* __USBAUDIO_H */
-- 
2.7.4

Re: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[Greg KH]

On Wed, Jun 17, 2020 at 10:55:30AM +0900, JaeHun Jung wrote:
> In mobile, a co-processor is used when using USB audio
> to improve power consumption.
> hooking is required for sync-up when operating
> the co-processor. So register call-back function.
> The main operation of the call-back function is as follows:
> - Initialize the co-processor by transmitting data
>   when initializing.
> - Change the co-processor setting value through
>   the interface function.
> - Configure sampling rate
> - pcm open/close
> 
> Bug: 156315379
> 
> Change-Id: I32e1dd408e64aaef68ee06c480c4b4d4c95546dc

No need for Bug or Change-Id on patches submitted to us, same for the
odd "ANDROID:" in the subject.

> Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
> ---
>  sound/usb/card.c     | 16 ++++++++++++++++
>  sound/usb/card.h     |  1 +
>  sound/usb/clock.c    |  5 +++++
>  sound/usb/pcm.c      | 33 +++++++++++++++++++++++++++++++++
>  sound/usb/usbaudio.h | 30 ++++++++++++++++++++++++++++++
>  5 files changed, 85 insertions(+)

Did you run scripts/get_maintainer.pl on this patch to determine that
maybe the alsa-devel list should also be needed?



> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index fd6fd17..2f3fa14 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -111,6 +111,7 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
>  static DEFINE_MUTEX(register_mutex);
>  static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
>  static struct usb_driver usb_audio_driver;
> +struct snd_usb_audio_vendor_ops *usb_audio_ops;
>  
>  /*
>   * disconnect streams
> @@ -210,6 +211,12 @@ static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int int
>  	return 0;
>  }
>  
> +void snd_set_vender_interface(struct snd_usb_audio_vendor_ops *vendor_ops)
> +{
> +	usb_audio_ops = vendor_ops;
> +}
> +EXPORT_SYMBOL_GPL(snd_set_vender_interface);

You are exporting a lot of new symbols, but you have no user of these
symbols, which is not allowed, as you know.  Please also post your user
of them so we can see if you are doing things correctly or not.

Also, only one set of "vendor ops" does not make any sense at all, this
needs to be on a per-host-controller basis, right?  If so, why is this
all in the sound driver?

thanks,

greg k-h

Re: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[Greg KH]

On Wed, Jun 17, 2020 at 07:17:38AM +0200, Greg KH wrote:
> On Wed, Jun 17, 2020 at 10:55:30AM +0900, JaeHun Jung wrote:
> > In mobile, a co-processor is used when using USB audio
> > to improve power consumption.
> > hooking is required for sync-up when operating
> > the co-processor. So register call-back function.
> > The main operation of the call-back function is as follows:
> > - Initialize the co-processor by transmitting data
> >   when initializing.
> > - Change the co-processor setting value through
> >   the interface function.
> > - Configure sampling rate
> > - pcm open/close
> > 
> > Bug: 156315379
> > 
> > Change-Id: I32e1dd408e64aaef68ee06c480c4b4d4c95546dc
> 
> No need for Bug or Change-Id on patches submitted to us, same for the
> odd "ANDROID:" in the subject.
> 
> > Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
> > ---
> >  sound/usb/card.c     | 16 ++++++++++++++++
> >  sound/usb/card.h     |  1 +
> >  sound/usb/clock.c    |  5 +++++
> >  sound/usb/pcm.c      | 33 +++++++++++++++++++++++++++++++++
> >  sound/usb/usbaudio.h | 30 ++++++++++++++++++++++++++++++
> >  5 files changed, 85 insertions(+)
> 
> Did you run scripts/get_maintainer.pl on this patch to determine that
> maybe the alsa-devel list should also be needed?
> 
> 
> 
> > 
> > diff --git a/sound/usb/card.c b/sound/usb/card.c
> > index fd6fd17..2f3fa14 100644
> > --- a/sound/usb/card.c
> > +++ b/sound/usb/card.c
> > @@ -111,6 +111,7 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
> >  static DEFINE_MUTEX(register_mutex);
> >  static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
> >  static struct usb_driver usb_audio_driver;
> > +struct snd_usb_audio_vendor_ops *usb_audio_ops;
> >  
> >  /*
> >   * disconnect streams
> > @@ -210,6 +211,12 @@ static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int int
> >  	return 0;
> >  }
> >  
> > +void snd_set_vender_interface(struct snd_usb_audio_vendor_ops *vendor_ops)
> > +{
> > +	usb_audio_ops = vendor_ops;
> > +}
> > +EXPORT_SYMBOL_GPL(snd_set_vender_interface);
> 
> You are exporting a lot of new symbols, but you have no user of these
> symbols, which is not allowed, as you know.  Please also post your user
> of them so we can see if you are doing things correctly or not.
> 
> Also, only one set of "vendor ops" does not make any sense at all, this
> needs to be on a per-host-controller basis, right?  If so, why is this
> all in the sound driver?

Also, your api is making a lot of assumptions about the running system,
there seems to not be any way to always "know" what bus/device the
callbacks are being used for in many places.

Why not just add the needed functionality to the sound driver itself
instead of trying to rely on these odd "callbacks"?

thanks,

greg k-h

RE: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[정재훈]

> -----Original Message-----
> From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-
> owner@vger.kernel.org] On Behalf Of Greg KH
> Sent: Wednesday, June 17, 2020 4:53 PM
> To: JaeHun Jung
> Cc: linux-usb@vger.kernel.org
> Subject: Re: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface
> 
> On Wed, Jun 17, 2020 at 07:17:38AM +0200, Greg KH wrote:
> > On Wed, Jun 17, 2020 at 10:55:30AM +0900, JaeHun Jung wrote:
> > > In mobile, a co-processor is used when using USB audio to improve
> > > power consumption.
> > > hooking is required for sync-up when operating the co-processor. So
> > > register call-back function.
> > > The main operation of the call-back function is as follows:
> > > - Initialize the co-processor by transmitting data
> > >   when initializing.
> > > - Change the co-processor setting value through
> > >   the interface function.
> > > - Configure sampling rate
> > > - pcm open/close
> > >
> > > Bug: 156315379
> > >
> > > Change-Id: I32e1dd408e64aaef68ee06c480c4b4d4c95546dc
> >
> > No need for Bug or Change-Id on patches submitted to us, same for the
> > odd "ANDROID:" in the subject.
> >

Ok, I will delete it.

> > > Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
> > > ---
> > >  sound/usb/card.c     | 16 ++++++++++++++++
> > >  sound/usb/card.h     |  1 +
> > >  sound/usb/clock.c    |  5 +++++
> > >  sound/usb/pcm.c      | 33 +++++++++++++++++++++++++++++++++
> > >  sound/usb/usbaudio.h | 30 ++++++++++++++++++++++++++++++
> > >  5 files changed, 85 insertions(+)
> >
> > Did you run scripts/get_maintainer.pl on this patch to determine that
> > maybe the alsa-devel list should also be needed?
> >

Yes, it was sent looking for maintainer of sound/usb.
This callbacks is for sync with Audio Core.
So, I was implement on sound/usb.

> >
> >
> > >
> > > diff --git a/sound/usb/card.c b/sound/usb/card.c index
> > > fd6fd17..2f3fa14 100644
> > > --- a/sound/usb/card.c
> > > +++ b/sound/usb/card.c
> > > @@ -111,6 +111,7 @@ MODULE_PARM_DESC(skip_validation, "Skip unit
> > > descriptor validation (default: no)  static
> > > DEFINE_MUTEX(register_mutex);  static struct snd_usb_audio
> > > *usb_chip[SNDRV_CARDS];  static struct usb_driver usb_audio_driver;
> > > +struct snd_usb_audio_vendor_ops *usb_audio_ops;
> > >
> > >  /*
> > >   * disconnect streams
> > > @@ -210,6 +211,12 @@ static int snd_usb_create_stream(struct
> snd_usb_audio *chip, int ctrlif, int int
> > >  	return 0;
> > >  }
> > >
> > > +void snd_set_vender_interface(struct snd_usb_audio_vendor_ops
> > > +*vendor_ops) {
> > > +	usb_audio_ops = vendor_ops;
> > > +}
> > > +EXPORT_SYMBOL_GPL(snd_set_vender_interface);
> >
> > You are exporting a lot of new symbols, but you have no user of these
> > symbols, which is not allowed, as you know.  Please also post your
> > user of them so we can see if you are doing things correctly or not.
> >

Yes, I know.
This is called from Audio core module.
Audio related drivers associated with this module cannot disclose because
of security.
I think this is true of other vendors as well.

> > Also, only one set of "vendor ops" does not make any sense at all,
> > this needs to be on a per-host-controller basis, right?  If so, why is
> > this all in the sound driver?
> 

Currently, this interface is only for USB audio. USB information is that is
has in the xhci host driver.
When USB audio is connected, F/W of audio core performs the control of USB
host for low power.

> Also, your api is making a lot of assumptions about the running system,
> there seems to not be any way to always "know" what bus/device the
> callbacks are being used for in many places.

This is only used in limited scenarios. And the information of USB host get
through from exynos_usb_audio driver.

> 
> Why not just add the needed functionality to the sound driver itself
> instead of trying to rely on these odd "callbacks"?

Audio core operates in F/W and is module.
Because there are many connected modules, it is cannot on built-in and
module to implement the non-callbacks

> 
> thanks,
> 
> greg k-h

Re: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface

[Greg KH]

On Wed, Jun 17, 2020 at 06:10:39PM +0900, ������ wrote:
> 
> 
> > -----Original Message-----
> > From: linux-usb-owner@vger.kernel.org [mailto:linux-usb-
> > owner@vger.kernel.org] On Behalf Of Greg KH
> > Sent: Wednesday, June 17, 2020 4:53 PM
> > To: JaeHun Jung
> > Cc: linux-usb@vger.kernel.org
> > Subject: Re: [PATCH] ANDROID: sound: usb: Add vendor's hooking interface
> > 
> > On Wed, Jun 17, 2020 at 07:17:38AM +0200, Greg KH wrote:
> > > On Wed, Jun 17, 2020 at 10:55:30AM +0900, JaeHun Jung wrote:
> > > > In mobile, a co-processor is used when using USB audio to improve
> > > > power consumption.
> > > > hooking is required for sync-up when operating the co-processor. So
> > > > register call-back function.
> > > > The main operation of the call-back function is as follows:
> > > > - Initialize the co-processor by transmitting data
> > > >   when initializing.
> > > > - Change the co-processor setting value through
> > > >   the interface function.
> > > > - Configure sampling rate
> > > > - pcm open/close
> > > >
> > > > Bug: 156315379
> > > >
> > > > Change-Id: I32e1dd408e64aaef68ee06c480c4b4d4c95546dc
> > >
> > > No need for Bug or Change-Id on patches submitted to us, same for the
> > > odd "ANDROID:" in the subject.
> > >
> 
> Ok, I will delete it.
> 
> > > > Signed-off-by: JaeHun Jung <jh0801.jung@samsung.com>
> > > > ---
> > > >  sound/usb/card.c     | 16 ++++++++++++++++
> > > >  sound/usb/card.h     |  1 +
> > > >  sound/usb/clock.c    |  5 +++++
> > > >  sound/usb/pcm.c      | 33 +++++++++++++++++++++++++++++++++
> > > >  sound/usb/usbaudio.h | 30 ++++++++++++++++++++++++++++++
> > > >  5 files changed, 85 insertions(+)
> > >
> > > Did you run scripts/get_maintainer.pl on this patch to determine that
> > > maybe the alsa-devel list should also be needed?
> > >
> 
> Yes, it was sent looking for maintainer of sound/usb.
> This callbacks is for sync with Audio Core.
> So, I was implement on sound/usb.
> 
> > >
> > >
> > > >
> > > > diff --git a/sound/usb/card.c b/sound/usb/card.c index
> > > > fd6fd17..2f3fa14 100644
> > > > --- a/sound/usb/card.c
> > > > +++ b/sound/usb/card.c
> > > > @@ -111,6 +111,7 @@ MODULE_PARM_DESC(skip_validation, "Skip unit
> > > > descriptor validation (default: no)  static
> > > > DEFINE_MUTEX(register_mutex);  static struct snd_usb_audio
> > > > *usb_chip[SNDRV_CARDS];  static struct usb_driver usb_audio_driver;
> > > > +struct snd_usb_audio_vendor_ops *usb_audio_ops;
> > > >
> > > >  /*
> > > >   * disconnect streams
> > > > @@ -210,6 +211,12 @@ static int snd_usb_create_stream(struct
> > snd_usb_audio *chip, int ctrlif, int int
> > > >  	return 0;
> > > >  }
> > > >
> > > > +void snd_set_vender_interface(struct snd_usb_audio_vendor_ops
> > > > +*vendor_ops) {
> > > > +	usb_audio_ops = vendor_ops;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(snd_set_vender_interface);
> > >
> > > You are exporting a lot of new symbols, but you have no user of these
> > > symbols, which is not allowed, as you know.  Please also post your
> > > user of them so we can see if you are doing things correctly or not.
> > >
> 
> Yes, I know.
> This is called from Audio core module.
> Audio related drivers associated with this module cannot disclose because
> of security.

What do you mean?  The license of the code is GPL version 2, so there is
no "security" reason to not publish it.

> I think this is true of other vendors as well.

What other vendor needs these hooks?

> > > Also, only one set of "vendor ops" does not make any sense at all,
> > > this needs to be on a per-host-controller basis, right?  If so, why is
> > > this all in the sound driver?
> > 
> 
> Currently, this interface is only for USB audio. USB information is that is
> has in the xhci host driver.
> When USB audio is connected, F/W of audio core performs the control of USB
> host for low power.

But that's not how these hooks are being created, you need to properly
handle any USB bus type.  As-is these will not work correctly.

> > Also, your api is making a lot of assumptions about the running system,
> > there seems to not be any way to always "know" what bus/device the
> > callbacks are being used for in many places.
> 
> This is only used in limited scenarios. And the information of USB host get
> through from exynos_usb_audio driver.

But that's not what these hooks show.

Again, please publish all of the code, we can not just add random kernel
hooks (that aren't even correct), without having a user of the code.

Would you want to have to maintain such a system?

> > Why not just add the needed functionality to the sound driver itself
> > instead of trying to rely on these odd "callbacks"?
> 
> Audio core operates in F/W and is module.
> Because there are many connected modules, it is cannot on built-in and
> module to implement the non-callbacks

I do not understand, sorry.  Perhaps the code that uses the hooks would
better explain this.

thanks,

greg k-h