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

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@quicinc.com

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