/dev/random - having a (trivial) coding problem

[Heusden, Folkert van]

See this program:

int main(int argc, char *argv[])
{
        int h;
        char buffer[16];
        int nbytes=16,nbits=16*8;
        int nin;

        h=open("/dev/random", O_RDONLY);
        if (h==-1) exit(1);

        /* see how many bits there are in it */
        printf("returned: %d\n", ioctl(h, RNDGETENTCNT, &nin));
        printf("current number of bits: %d\n", nin);

        /* add some */
        printf("returned: %d\n", ioctl(h, RNDADDENTROPY, buffer, (int
*)&nbits, (int *)&nbytes));

        /* see it it succeeded */
        printf("returned: %d\n", ioctl(h, RNDGETENTCNT, &nin));
        printf("current number of bits: %d\n", nin);

return 0;
}

it always fails!
But if I read the code for /dev/random correctly:
        case RNDADDENTROPY:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                p = (int *) arg;
                if (get_user(ent_count, p++))
                        return -EFAULT;
                if (ent_count < 0)
                        return -EINVAL;
                if (get_user(size, p++))
                        return -EFAULT;
                retval = random_write(file, (const char *) p,
                                      size, &file->f_pos);
                if (retval < 0)
                        return retval;
                credit_entropy_store(random_state, ent_count);

I did the right thing.
Didn't I? Aren't the ioctl-parameters in this case pointer to int, pointer
to int (ent_count) and another (to size)?