diff mbox series

[RFC,10/14] sound: usb: card: Check for support for requested audio format

Message ID 20221223233200.26089-11-quic_wcheng@quicinc.com (mailing list archive)
State Superseded
Headers show
Series Introduce QC USB SND audio offloading support | expand

Commit Message

Wesley Cheng Dec. 23, 2022, 11:31 p.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 for when playback is
initiated by the ASoC USB backend path.

Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
---
 sound/usb/card.c | 19 +++++++++++++++++++
 sound/usb/card.h |  3 +++
 2 files changed, 22 insertions(+)

Comments

Greg KH Dec. 24, 2022, 8:59 a.m. UTC | #1
On Fri, Dec 23, 2022 at 03:31:56PM -0800, 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 for when playback is
> initiated by the ASoC USB backend path.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>  sound/usb/card.c | 19 +++++++++++++++++++
>  sound/usb/card.h |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 396e5a34e23b..9b8d2ed308c8 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -133,6 +133,25 @@ int snd_usb_unregister_vendor_ops(void)
>  }
>  EXPORT_SYMBOL_GPL(snd_usb_unregister_vendor_ops);
>  
> +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
> +			struct snd_pcm_hw_params *params, int direction)
> +{
> +	struct snd_usb_stream *as;
> +	struct snd_usb_substream *subs = NULL;
> +	const struct audioformat *fmt;
> +
> +	if (usb_chip[card_idx] && enable[card_idx]) {
> +		list_for_each_entry(as, &usb_chip[card_idx]->pcm_list, list) {
> +			subs = &as->substream[direction];
> +			fmt = find_substream_format(subs, params);
> +			if (fmt)
> +				return as;
> +		}
> +	}

Where is the locking here?  How can you walk a list that can be changed
as you walk it?

And what about reference counting?  You are returning a pointer to a
structure, who now "owns" it?  What happens if it is removed from the
system after you return it?

> +	return 0;

Didn't sparse complain about this?  You can't return "0" as a pointer,
it should be NULL.

Always run basic tools like sparse on code before submitting it so that
we don't have to find errors like this.

thanks,

greg k-h
Wesley Cheng Dec. 27, 2022, 9:07 p.m. UTC | #2
Hi Greg,

On 12/24/2022 12:59 AM, Greg KH wrote:
> On Fri, Dec 23, 2022 at 03:31:56PM -0800, 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 for when playback is
>> initiated by the ASoC USB backend path.
>>
>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>> ---
>>   sound/usb/card.c | 19 +++++++++++++++++++
>>   sound/usb/card.h |  3 +++
>>   2 files changed, 22 insertions(+)
>>
>> diff --git a/sound/usb/card.c b/sound/usb/card.c
>> index 396e5a34e23b..9b8d2ed308c8 100644
>> --- a/sound/usb/card.c
>> +++ b/sound/usb/card.c
>> @@ -133,6 +133,25 @@ int snd_usb_unregister_vendor_ops(void)
>>   }
>>   EXPORT_SYMBOL_GPL(snd_usb_unregister_vendor_ops);
>>   
>> +struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
>> +			struct snd_pcm_hw_params *params, int direction)
>> +{
>> +	struct snd_usb_stream *as;
>> +	struct snd_usb_substream *subs = NULL;
>> +	const struct audioformat *fmt;
>> +
>> +	if (usb_chip[card_idx] && enable[card_idx]) {
>> +		list_for_each_entry(as, &usb_chip[card_idx]->pcm_list, list) {
>> +			subs = &as->substream[direction];
>> +			fmt = find_substream_format(subs, params);
>> +			if (fmt)
>> +				return as;
>> +		}
>> +	}
> 
> Where is the locking here?  How can you walk a list that can be changed
> as you walk it?
> 
> And what about reference counting?  You are returning a pointer to a
> structure, who now "owns" it?  What happens if it is removed from the
> system after you return it?
> 
>> +	return 0;
> 
> Didn't sparse complain about this?  You can't return "0" as a pointer,
> it should be NULL.
> 
> Always run basic tools like sparse on code before submitting it so that
> we don't have to find errors like this.
> 

Got it...I didn't get a chance to run that, but will do it on future 
submissions.  Will also address the locking and pointer reference you 
mentioned.

Thanks
Wesley Cheng
diff mbox series

Patch

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 396e5a34e23b..9b8d2ed308c8 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -133,6 +133,25 @@  int snd_usb_unregister_vendor_ops(void)
 }
 EXPORT_SYMBOL_GPL(snd_usb_unregister_vendor_ops);
 
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction)
+{
+	struct snd_usb_stream *as;
+	struct snd_usb_substream *subs = NULL;
+	const struct audioformat *fmt;
+
+	if (usb_chip[card_idx] && enable[card_idx]) {
+		list_for_each_entry(as, &usb_chip[card_idx]->pcm_list, list) {
+			subs = &as->substream[direction];
+			fmt = find_substream_format(subs, params);
+			if (fmt)
+				return as;
+		}
+	}
+
+	return 0;
+}
+
 /*
  * disconnect streams
  * called from usb_audio_disconnect()
diff --git a/sound/usb/card.h b/sound/usb/card.h
index a785bb256b0d..d4936b6054fc 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -213,4 +213,7 @@  struct snd_usb_vendor_ops {
 
 int snd_usb_register_vendor_ops(struct snd_usb_vendor_ops *ops);
 int snd_usb_unregister_vendor_ops(void);
+
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction);
 #endif /* __USBAUDIO_CARD_H */