trezor-firmware/extmod/modtrezormsg/modtrezormsg-stmhal.h

void msg_init(void)
{
}

const uint8_t *msg_recv(void)
{
    return 0;
}

int msg_send(uint8_t *buf, size_t len)
{
    return -1;
}

uint32_t msg_poll_ui_event(void)
{
    return 0;
}