pkg/tinydtls: fix compilation with sock_async

[maribu]

Contribution description

When module sock_async is used but sock_async_event is not, compilation previously failed. This fixes the issue.

Testing procedure

In master

USEMODULE=sock_async make -C tests/net/nanocoap_cli BOARD=native64 -j
[...]
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c: In function ‘sock_dtls_set_cb’:
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c:1067:9: error: unknown type name ‘sock_async_ctx_t’; did you mean ‘sock_async_flags_t’?
 1067 |         sock_async_ctx_t *ctx = sock_dtls_get_async_ctx(sock);
      |         ^~~~~~~~~~~~~~~~
      |         sock_async_flags_t
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c:1067:33: error: implicit declaration of function ‘sock_dtls_get_async_ctx’ [-Werror=implicit-function-declaration]
 1067 |         sock_async_ctx_t *ctx = sock_dtls_get_async_ctx(sock);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c:1067:33: error: initialization of ‘int *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c:1068:16: error: request for member ‘queue’ in something not a structure or union
 1068 |         if (ctx->queue) {
      |                ^~
/home/[email protected]/Repos/software/RIOT/master/pkg/tinydtls/contrib/sock_dtls.c:1069:52: error: request for member ‘queue’ in something not a structure or union
 1069 |             sock_udp_event_init(sock->udp_sock, ctx->queue, _udp_cb, sock);
      |                                                    ^~
cc1: all warnings being treated as errors

This PR

USEMODULE=sock_async make -C tests/net/nanocoap_cli BOARD=native64 -j
[...]
   text	  data	   bss	   dec	   hex	filename
 265870	  4328	154128	424326	 67986	/home/[email protected]/Repos/software/RIOT/master/tests/net/nanocoap_cli/bin/native64/tests_nanocoap_cli.elf
make: Leaving directory '/home/[email protected]/Repos/software/RIOT/master/tests/net/nanocoap_cli'

Issues/PRs references

None

[riot-ci]

Murdock results

✔️ PASSED

e08fb49 pkg/tinydtls: fix compilation with sock_async

Success	Failures	Total	Runtime
10246	0	10248	16m:51s

Artifacts

• Documentation preview

[benpicco]

Wait doesn't sock_udp_set_cb() also require sock_async?

[maribu]

Yes, but what is hidden behind condition compilation now is related to sock_async_event rather than sock_async.

The difference is that with sock_async_event an event handler does perform the actual callback (hence, a user defined thread), while sock_async will perform the callback in an implementation defined context.