snd_ctl_event
if (count < sizeof(struct snd_ctl_event))
while (count >= sizeof(struct snd_ctl_event)) {
struct snd_ctl_event ev;
if (copy_to_user(buffer, &ev, sizeof(struct snd_ctl_event))) {
buffer += sizeof(struct snd_ctl_event);
count -= sizeof(struct snd_ctl_event);
result += sizeof(struct snd_ctl_event);