Re: [PATCH v3 09/28] sound: usb: card: Introduce USB SND platform op callbacks

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On 09.03.23 00:57, Wesley Cheng wrote:
Allow for different platforms to be notified on USB SND connect/disconnect
seqeunces.  This allows for platform USB SND modules to properly initialize
and populate internal structures with references to the USB SND chip
device.

Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
  sound/usb/card.c | 36 ++++++++++++++++++++++++++++++++++++
  sound/usb/card.h | 20 ++++++++++++++++++++
  2 files changed, 56 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 26268ffb8274..9bcbaa0c0a55 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -117,6 +117,30 @@ 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;
+static struct snd_usb_platform_ops *platform_ops;
+
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
+{
+	if (platform_ops)
+		return -EEXIST;
+
+	mutex_lock(&register_mutex);
+	platform_ops = ops;
+	mutex_unlock(&register_mutex);

This looks _highly_ suspicious.
Why does the assignment need a lock, but the check does not?

	Regards
		Oliver



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