__HOST_GEN_ECDH_KEY__ usage?

`__HOST_GEN_ECDH_KEY__` is a preprocessor macro that is used in cryptography applications to generate an Elliptic Curve Diffie-Hellman (ECDH) key pair on the host side. ECDH is a key exchange algorithm that allows two parties to securely establish a shared secret key over an insecure channel.

To use `__HOST_GEN_ECDH_KEY__`, you need to include a cryptography library that supports ECDH key generation. The macro is typically used in a program that runs on the host computer, and it generates a key pair that can be used to securely communicate with a device that supports ECDH.

Here is an example of how to use `__HOST_GEN_ECDH_KEY__`:

#include <crypto/ecdh.h>

ECDH_KEYPAIR __HOST_GEN_ECDH_KEY__(void);

int main()
{
    ECDH_KEYPAIR keypair = __HOST_GEN_ECDH_KEY__();
    // Use the keypair to securely communicate with the device
    // ...
    return 0;
}

Note that the implementation of `__HOST_GEN_ECDH_KEY__` may vary depending on the cryptography library you are using. You should consult the documentation of the library for specific instructions on how to use the macro.