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    SubjectRe: [RFC PATCH 04/14] sound: usb: card: Introduce USB SND vendor op callbacks
    Hi,

    On Sat, 24 Dec 2022 at 01:33, Wesley Cheng <quic_wcheng@quicinc.com> wrote:
    >
    > Allow for different vendors to be notified on USB SND connect/disconnect
    > seqeunces. This allows for vendor USB SND modules to properly initialize
    > and populate internal structures with references to the USB SND chip
    > device.

    The commit message definitely needs some improvement. We do not notify
    vendors on SND connect/disconnect events.


    >
    > Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
    > ---
    > sound/usb/card.c | 22 ++++++++++++++++++++++
    > sound/usb/card.h | 7 +++++++
    > 2 files changed, 29 insertions(+)
    >
    > diff --git a/sound/usb/card.c b/sound/usb/card.c
    > index 26268ffb8274..212f55a7683c 100644
    > --- a/sound/usb/card.c
    > +++ b/sound/usb/card.c
    > @@ -117,6 +117,21 @@ 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_vendor_ops *vendor_ops;
    > +
    > +int snd_usb_register_vendor_ops(struct snd_usb_vendor_ops *ops)

    platform ops?

    > +{
    > + vendor_ops = ops;
    > + return 0;
    > +}
    > +EXPORT_SYMBOL_GPL(snd_usb_register_vendor_ops);

    What happens if several platforms try to register different ops? I saw
    from the patch 09/14 that you register these ops unconditionally. If
    other devices follow your approach there is an obvious conflict.

    > +
    > +int snd_usb_unregister_vendor_ops(void)
    > +{
    > + vendor_ops = NULL;
    > + return 0;
    > +}
    > +EXPORT_SYMBOL_GPL(snd_usb_unregister_vendor_ops);
    >
    > /*
    > * disconnect streams
    > @@ -910,6 +925,10 @@ static int usb_audio_probe(struct usb_interface *intf,
    > usb_set_intfdata(intf, chip);
    > atomic_dec(&chip->active);
    > mutex_unlock(&register_mutex);
    > +
    > + if (vendor_ops->connect_cb)
    > + vendor_ops->connect_cb(intf, chip);
    > +
    > return 0;
    >
    > __error:
    > @@ -943,6 +962,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
    > if (chip == USB_AUDIO_IFACE_UNUSED)
    > return;
    >
    > + if (vendor_ops->disconnect_cb)
    > + vendor_ops->disconnect_cb(intf);
    > +
    > card = chip->card;
    >
    > mutex_lock(&register_mutex);
    > diff --git a/sound/usb/card.h b/sound/usb/card.h
    > index 40061550105a..a785bb256b0d 100644
    > --- a/sound/usb/card.h
    > +++ b/sound/usb/card.h
    > @@ -206,4 +206,11 @@ struct snd_usb_stream {
    > struct list_head list;
    > };
    >
    > +struct snd_usb_vendor_ops {
    > + void (*connect_cb)(struct usb_interface *intf, struct snd_usb_audio *chip);
    > + void (*disconnect_cb)(struct usb_interface *intf);
    > +};
    > +
    > +int snd_usb_register_vendor_ops(struct snd_usb_vendor_ops *ops);
    > +int snd_usb_unregister_vendor_ops(void);
    > #endif /* __USBAUDIO_CARD_H */



    --
    With best wishes

    Dmitry

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