On Thu, Mar 24, 2022 at 09:33:40AM +0100, Greg Kroah-Hartman wrote:
> On Thu, Mar 24, 2022 at 05:10:42PM +0900, Oh Eomji wrote:
> > In mobile, a co-processor can be used with USB audio to improve power
> > consumption. To support this type of hardware, hooks need to be added
> > to the USB audio subsystem to be able to call into the hardware when
> > needed.
> >
> > The main operation of the call-backs are:
> > - Initialize the co-processor by transmitting data when initializing.
> > - Change the co-processor setting value through the interface
> > function.
> > - Configure sampling rate
> > - pcm open/close
> > - other housekeeping
> >
> > Known issues:
> > - This only supports one set of callback hooks, meaning that this only
> > works if there is one type of USB controller in the system. This
> > should be changed to be a per-host-controller interface instead of
> > one global set of callbacks.
> >
> > Signed-off-by: JaeHun Jung <jh0801.jung@xxxxxxxxxxx>
> > Signed-off-by: Oh Eomji <eomji.oh@xxxxxxxxxxx>
> > ---
> > sound/usb/card.c | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > sound/usb/card.h | 20 +++++++++
> > sound/usb/usbaudio.h | 45 +++++++++++++++++++
> > 3 files changed, 184 insertions(+)
> >
> > diff --git a/sound/usb/card.c b/sound/usb/card.c
> > index 3769622..bd59311 100644
> > --- a/sound/usb/card.c
> > +++ b/sound/usb/card.c
> > @@ -117,6 +117,117 @@ 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_audio_vendor_ops *usb_vendor_ops;
> > +
> > +int snd_vendor_set_ops(struct snd_usb_audio_vendor_ops *ops)
> > +{
> > + if ((!ops->connect) ||
> > + (!ops->disconnect) ||
> > + (!ops->set_interface) ||
> > + (!ops->set_rate) ||
> > + (!ops->set_pcm_buf) ||
> > + (!ops->set_pcm_intf) ||
> > + (!ops->set_pcm_connection) ||
> > + (!ops->set_pcm_binterval) ||
> > + (!ops->usb_add_ctls))
> > + return -EINVAL;
> > +
> > + usb_vendor_ops = ops;
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(snd_vendor_set_ops);
> > +
> > +struct snd_usb_audio_vendor_ops *snd_vendor_get_ops(void)
> > +{
> > + return usb_vendor_ops;
> > +}
>
> This is the function you need to fix up, and add proper reference
> counting to, in order to solve your "this breaks with multiple USB
> controllers" problem. So this really should not be all that difficult
> of a task. Why has it taken years to do so?
>
> thanks,
>
> greg k-h
>
Hi,
Is that mean the scenario when two or more usb audio devices are
connected through the hub?
Thanks,
Eomji Oh
