vv_callback
if (dev->vv_data && dev->vv_callback)
dev->vv_callback(dev,isr);
if (dev->vv_data && dev->vv_callback)
dev->vv_callback(dev,isr);
dev->vv_callback = &vv_callback;
dev->vv_callback = NULL;
void (*vv_callback)(struct saa7146_dev *dev, unsigned long status);