wiznet / rp2040-hat-lwip-c Goto Github PK

I'm building a project where I hope to use the W5100S with the LWIP IP stack, and
noticed gcc complaining about several set but unused (never read) variables.

For example, in w5x00_lwip.c:110:

1. send_len is set but never used.
2. The crc calculated by ethernet_frame_crc is never used.

The example code seems to work, so I assume (2) is okay because the W5100S calculates the CRC?

Is this repository the best reference for using the W5100S with LWIP, or should I be looking elsewhere?

err_t netif_output(struct netif *netif, struct pbuf *p)
{
    uint32_t send_len = 0;
    uint32_t tot_len = 0;

    memset(tx_frame, 0x00, sizeof(tx_frame));

    for (struct pbuf *q = p; q != NULL; q = q->next)
    {
        memcpy(tx_frame + tot_len, q->payload, q->len);

        tot_len += q->len;

        if (q->len == q->tot_len)
        {
            break;
        }
    }

    if (tot_len < 60)
    {
        // pad
        tot_len = 60;
    }

    uint32_t crc = ethernet_frame_crc(tx_frame, tot_len);  // crc set, never used

    send_len = send_lwip(0, tx_frame, tot_len);  // send_len set, never used

    return ERR_OK;
}

This is really a question, as a result of a question on the WIZnet forum (topic 10579).
Why does the code in wizchip_initialize() block until LINK UP is established? So when called if the ethernet cable is unplugged or the switch is down the call would not return. See code at line 211 here: https://github.com/Wiznet/RP2040-HAT-LWIP-C/blob/main/port/ioLibrary_Driver/src/w5x00_spi.c

Would it do any harm to just return the LINK status rather than looping to wait for LINK_UP? or can it just return no matter what the LINK status is?
Unplugging and re-plugging the cable back in once the network is up results in full recovery.

This call is made in nearly all of the example programs.