Well, I assume you have found this starting point:

linux/arch/arm/special/empeg_mixer.c:

case EMPEG_MIXER_SET_EQ:
{
struct empeg_eq_section_t sections[20];
#if MIXER_DEBUG
printk(MIXER_NAME
": mixer_ioctl EMPEG_MIXER_SET_EQ %08lx\n",
arg);
#endif

copy_from_user_ret((void *) sections, (const void *) arg,
sizeof(sections), -EFAULT);

empeg_mixer_eq_set(sections);
empeg_mixer_eq_apply();
return 0;
}