diff mbox series

[v13,32/53] ALSA: usb-audio: Check for support for requested audio format

Message ID 20240203023645.31105-33-quic_wcheng@quicinc.com
State Superseded
Headers show
Series Introduce QC USB SND audio offloading support | expand

Commit Message

Wesley Cheng Feb. 3, 2024, 2:36 a.m. UTC
Allow for checks on a specific USB audio device to see if a requested PCM
format is supported.  This is needed for support when playback is
initiated by the ASoC USB backend path.

Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
---
 sound/usb/card.c | 40 ++++++++++++++++++++++++++++++++++++++++
 sound/usb/card.h | 11 +++++++++++
 2 files changed, 51 insertions(+)

Comments

Takashi Iwai Feb. 6, 2024, 1:12 p.m. UTC | #1
On Sat, 03 Feb 2024 03:36:24 +0100,
Wesley Cheng wrote:
> 
> Allow for checks on a specific USB audio device to see if a requested PCM
> format is supported.  This is needed for support when playback is
> initiated by the ASoC USB backend path.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>

Just cosmetic:

> +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
> +			struct snd_pcm_hw_params *params, int direction)
> +{
> +	struct snd_usb_audio *chip;
> +	struct snd_usb_substream *subs;
> +	struct snd_usb_stream *as;
> +	const struct audioformat *fmt;
> +
> +	/*
> +	 * Register mutex is held when populating and clearing usb_chip
> +	 * array.
> +	 */
> +	mutex_lock(&register_mutex);
> +	chip = usb_chip[card_idx];
> +	if (!chip) {
> +		mutex_unlock(&register_mutex);
> +		return NULL;
> +	}
> +
> +	if (enable[card_idx]) {
> +		list_for_each_entry(as, &chip->pcm_list, list) {
> +			subs = &as->substream[direction];
> +			fmt = snd_usb_find_substream_format(subs, params);
> +			if (fmt) {
> +				mutex_unlock(&register_mutex);
> +				return as;
> +			}
> +		}
> +	}
> +	mutex_unlock(&register_mutex);

I prefer having the single lock/unlock call pair, e.g.

	struct snd_usb_stream *as, *ret;

	ret = NULL;
	mutex_lock(&register_mutex);
	chip = usb_chip[card_idx];
	if (chip && enable[card_idx]) {
		list_for_each_entry(as, &chip->pcm_list, list) {
			subs = &as->substream[direction];
			if (snd_usb_find_substream_format(subs, params)) {
				ret = as;
				break;
			}
		}
	}
	mutex_unlock(&register_mutex);
	return ret;
}

In this case, we shouldn't reuse "as" for the return value since it
can be non-NULL after the loop end.


thanks,

Takashi
Greg KH Feb. 6, 2024, 2:50 p.m. UTC | #2
On Tue, Feb 06, 2024 at 02:12:44PM +0100, Takashi Iwai wrote:
> On Sat, 03 Feb 2024 03:36:24 +0100,
> Wesley Cheng wrote:
> > 
> > Allow for checks on a specific USB audio device to see if a requested PCM
> > format is supported.  This is needed for support when playback is
> > initiated by the ASoC USB backend path.
> > 
> > Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> 
> Just cosmetic:
> 
> > +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
> > +			struct snd_pcm_hw_params *params, int direction)
> > +{
> > +	struct snd_usb_audio *chip;
> > +	struct snd_usb_substream *subs;
> > +	struct snd_usb_stream *as;
> > +	const struct audioformat *fmt;
> > +
> > +	/*
> > +	 * Register mutex is held when populating and clearing usb_chip
> > +	 * array.
> > +	 */
> > +	mutex_lock(&register_mutex);
> > +	chip = usb_chip[card_idx];
> > +	if (!chip) {
> > +		mutex_unlock(&register_mutex);
> > +		return NULL;
> > +	}
> > +
> > +	if (enable[card_idx]) {
> > +		list_for_each_entry(as, &chip->pcm_list, list) {
> > +			subs = &as->substream[direction];
> > +			fmt = snd_usb_find_substream_format(subs, params);
> > +			if (fmt) {
> > +				mutex_unlock(&register_mutex);
> > +				return as;
> > +			}
> > +		}
> > +	}
> > +	mutex_unlock(&register_mutex);
> 
> I prefer having the single lock/unlock call pair, e.g.
> 
> 	struct snd_usb_stream *as, *ret;
> 
> 	ret = NULL;
> 	mutex_lock(&register_mutex);
> 	chip = usb_chip[card_idx];
> 	if (chip && enable[card_idx]) {
> 		list_for_each_entry(as, &chip->pcm_list, list) {
> 			subs = &as->substream[direction];
> 			if (snd_usb_find_substream_format(subs, params)) {
> 				ret = as;
> 				break;
> 			}
> 		}
> 	}
> 	mutex_unlock(&register_mutex);
> 	return ret;
> }
> 
> In this case, we shouldn't reuse "as" for the return value since it
> can be non-NULL after the loop end.

Why not just use guard(mutex) for this, making it all not an issue?

thanks,

greg k-h
Takashi Iwai Feb. 6, 2024, 2:53 p.m. UTC | #3
On Tue, 06 Feb 2024 15:50:21 +0100,
Greg KH wrote:
> 
> On Tue, Feb 06, 2024 at 02:12:44PM +0100, Takashi Iwai wrote:
> > On Sat, 03 Feb 2024 03:36:24 +0100,
> > Wesley Cheng wrote:
> > > 
> > > Allow for checks on a specific USB audio device to see if a requested PCM
> > > format is supported.  This is needed for support when playback is
> > > initiated by the ASoC USB backend path.
> > > 
> > > Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> > 
> > Just cosmetic:
> > 
> > > +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
> > > +			struct snd_pcm_hw_params *params, int direction)
> > > +{
> > > +	struct snd_usb_audio *chip;
> > > +	struct snd_usb_substream *subs;
> > > +	struct snd_usb_stream *as;
> > > +	const struct audioformat *fmt;
> > > +
> > > +	/*
> > > +	 * Register mutex is held when populating and clearing usb_chip
> > > +	 * array.
> > > +	 */
> > > +	mutex_lock(&register_mutex);
> > > +	chip = usb_chip[card_idx];
> > > +	if (!chip) {
> > > +		mutex_unlock(&register_mutex);
> > > +		return NULL;
> > > +	}
> > > +
> > > +	if (enable[card_idx]) {
> > > +		list_for_each_entry(as, &chip->pcm_list, list) {
> > > +			subs = &as->substream[direction];
> > > +			fmt = snd_usb_find_substream_format(subs, params);
> > > +			if (fmt) {
> > > +				mutex_unlock(&register_mutex);
> > > +				return as;
> > > +			}
> > > +		}
> > > +	}
> > > +	mutex_unlock(&register_mutex);
> > 
> > I prefer having the single lock/unlock call pair, e.g.
> > 
> > 	struct snd_usb_stream *as, *ret;
> > 
> > 	ret = NULL;
> > 	mutex_lock(&register_mutex);
> > 	chip = usb_chip[card_idx];
> > 	if (chip && enable[card_idx]) {
> > 		list_for_each_entry(as, &chip->pcm_list, list) {
> > 			subs = &as->substream[direction];
> > 			if (snd_usb_find_substream_format(subs, params)) {
> > 				ret = as;
> > 				break;
> > 			}
> > 		}
> > 	}
> > 	mutex_unlock(&register_mutex);
> > 	return ret;
> > }
> > 
> > In this case, we shouldn't reuse "as" for the return value since it
> > can be non-NULL after the loop end.
> 
> Why not just use guard(mutex) for this, making it all not an issue?

Heh, it's too new ;)
That should work gracefully, yes.


Takashi
diff mbox series

Patch

diff --git a/sound/usb/card.c b/sound/usb/card.c
index c0b312e264bf..11b827b7a2a5 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -162,6 +162,46 @@  int snd_usb_unregister_platform_ops(void)
 }
 EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);
 
+/*
+ * Checks to see if requested audio profile, i.e sample rate, # of
+ * channels, etc... is supported by the substream associated to the
+ * USB audio device.
+ */
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction)
+{
+	struct snd_usb_audio *chip;
+	struct snd_usb_substream *subs;
+	struct snd_usb_stream *as;
+	const struct audioformat *fmt;
+
+	/*
+	 * Register mutex is held when populating and clearing usb_chip
+	 * array.
+	 */
+	mutex_lock(&register_mutex);
+	chip = usb_chip[card_idx];
+	if (!chip) {
+		mutex_unlock(&register_mutex);
+		return NULL;
+	}
+
+	if (enable[card_idx]) {
+		list_for_each_entry(as, &chip->pcm_list, list) {
+			subs = &as->substream[direction];
+			fmt = snd_usb_find_substream_format(subs, params);
+			if (fmt) {
+				mutex_unlock(&register_mutex);
+				return as;
+			}
+		}
+	}
+	mutex_unlock(&register_mutex);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(snd_usb_find_suppported_substream);
+
 /*
  * disconnect streams
  * called from usb_audio_disconnect()
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 02e4ea898db5..ed4a664e24e5 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -217,4 +217,15 @@  struct snd_usb_platform_ops {
 
 int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
 int snd_usb_unregister_platform_ops(void);
+
+#if IS_ENABLED(CONFIG_SND_USB_AUDIO)
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction);
+#else
+static struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction)
+{
+	return NULL;
+}
+#endif /* IS_ENABLED(CONFIG_SND_USB_AUDIO) */
 #endif /* __USBAUDIO_CARD_H */