If you need to change and update a control in the interrupt routine, you can call snd_ctl_notify(). For example,

  snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer);

          

This function takes the card pointer, the event-mask, and the control id pointer for the notification. The event-mask specifies the types of notification, for example, in the above example, the change of control values is notified. The id pointer is the pointer of struct snd_ctl_elem_id to be notified. You can find some examples in es1938.c or es1968.c for hardware volume interrupts.