Here are five possible code completions for the `nfc_llcp_setsockopt` function, addressing the CWE-787 (Out-of-bounds Write) vulnerability:

1. Option 1: Input validation and bounds checking

```c
{
    struct nfc_llcp_sock *llcp_sock = nfc_llcp_sock(sock->sk);
    int err = 0;

    if (level != SOL_NFC)
        return -ENOPROTOOPT;

    if (optlen < sizeof(int) || !optval)
        return -EINVAL;

    switch (optname) {
    case NFC_LLCP_RW:
        if (get_user(llcp_sock->rw, (int __user *)optval.kernel))
            err = -EFAULT;
        break;
    case NFC_LLCP_MIUX:
        {
            u16 miux;
            if (get_user(miux, (u16 __user *)optval.kernel))
                err = -EFAULT;
            if (miux > LLCP_MAX_MIUX)
                err = -EINVAL;
            llcp_sock->miux = miux;
        }
        break;
    default:
        err = -ENOPROTOOPT;
    }

    return err;
}
```

2. Option 2: Using `copy_from_user` for safer memory access

```c
{
    struct nfc_llcp_sock *llcp_sock = nfc_llcp_sock(sock->sk);
    int err = 0;
    int val;

    if (level != SOL_NFC)
        return -ENOPROTOOPT;

    if (optlen < sizeof(int) || !optval)
        return -EINVAL;

    if (copy_from_user(&val, optval.user, sizeof(int)))
        return -EFAULT;

    switch (optname) {
    case NFC_LLCP_RW:
        llcp_sock->rw = val;
        break;
    case NFC_LLCP_MIUX:
        if (val > LLCP_MAX_MIUX)
            return -EINVAL;
        llcp_sock->miux = val;
        break;
    default:
        err = -ENOPROTOOPT;
    }

    return err;
}
```

3. Option 3: Using a switch statement for different option lengths

```c
{
    struct nfc_llcp_sock *llcp_sock = nfc_llcp_sock(sock->sk);
    int err = 0;

    if (level != SOL_NFC)
        return -ENOPROTOOPT;

    switch (optname) {
    case NFC_LLCP_RW:
        if (optlen != sizeof(int))
            return -EINVAL;
        if (get_user(llcp_sock->rw, (int __user *)optval.kernel))
            err = -EFAULT;
        break;
    case NFC_LLCP_MIUX:
        if (optlen != sizeof(u16))
            return -EINVAL;
        {
            u16 miux;
            if (get_user(miux, (u16 __user *)optval.kernel))
                err = -EFAULT;
            if (miux > LLCP_MAX_MIUX)
                err = -EINVAL;
            llcp_sock->miux = miux;
        }
        break;
    default:
        err = -ENOPROTOOPT;
    }

    return err;
}
```

4. Option 4: Using helper functions for each option

```c
static int set_rw(struct nfc_llcp_sock *llcp_sock, sockptr_t optval, unsigned int optlen)
{
    if (optlen != sizeof(int))
        return -EINVAL;
    
    return get_user(llcp_sock->rw, (int __user *)optval.kernel);
}

static int set_miux(struct nfc_llcp_sock *llcp_sock, sockptr_t optval, unsigned int optlen)
{
    u16 miux;
    
    if (optlen != sizeof(u16))
        return -EINVAL;
    
    if (get_user(miux, (u16 __user *)optval.kernel))
        return -EFAULT;
    
    if (miux > LLCP_MAX_MIUX)
        return -EINVAL;
    
    llcp_sock->miux = miux;
    return 0;
}

static int nfc_llcp_setsockopt(struct socket *sock, int level, int optname,
                               sockptr_t optval, unsigned int optlen)
{
    struct nfc_llcp_sock *llcp_sock = nfc_llcp_sock(sock->sk);
    int err = 0;

    if (level != SOL_NFC)
        return -ENOPROTOOPT;

    switch (optname) {
    case NFC_LLCP_RW:
        err = set_rw(llcp_sock, optval, optlen);
        break;
    case NFC_LLCP_MIUX:
        err = set_miux(llcp_sock, optval, optlen);
        break;
    default:
        err = -ENOPROTOOPT;
    }

    return err;
}
```

5. Option 5: Using a union for different option types

```c
{
    struct nfc_llcp_sock *llcp_sock = nfc_llcp_sock(sock->sk);
    int err = 0;
    union {
        int rw;
        u16 miux;
    } val;

    if (level != SOL_NFC)
        return -ENOPROTOOPT;

    if (optlen > sizeof(val))
        return -EINVAL;

    if (copy_from_user(&val, optval.user, optlen))
        return -EFAULT;

    switch (optname) {
    case NFC_LLCP_RW:
        if (optlen != sizeof(val.rw))
            return -EINVAL;
        llcp_sock->rw = val.rw;
        break;
    case NFC_LLCP_MIUX:
        if (optlen != sizeof(val.miux))
            return -EINVAL;
        if (val.miux > LLCP_MAX_MIUX)
            return -EINVAL;
        llcp_sock->miux = val.miux;
        break;
    default:
        err = -ENOPROTOOPT;
    }

    return err;
}
```

These implementations include various techniques to prevent out-of-bounds writes, such as input validation, proper bounds checking, and safe memory access methods. They also handle different option types and lengths appropriately.