snd_pcm_sframes_t snd_pcm_lib_read(struct snd_pcm_substream *substream, void __user *buf, snd_pcm_uframes_t size)
{
    ....
    return snd_pcm_lib_read1(substream, (unsigned long)buf, size, nonblock, snd_pcm_lib_read_transfer);
}

uint32_t hash_of_foo_ptr(struct foo_st *foo) {
   return (uint32_t)(((intptr_t)foo) * 613) ^ ((intptr_t)foo % 51043));
}