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@xxxxxxxxxxx>
---
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
