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

[Wesley Cheng]

Hi Dmitry,

On 12/24/2022 3:03 AM, Dmitry Baryshkov wrote:
> Hi,
>
> On Sat, 24 Dec 2022 at 01:33, Wesley Cheng <quic_wcheng@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> >   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?

Will change it.

> > +{
> > +       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.

Thank you for the review.

That is true.  I don't think there is a proper need to have multiple 
vendor ops being registered, so maybe just returning an error for if ops 
are already registered is sufficient.

Thanks
Wesley Cheng