tpm-be: update optional function pointers

QEMU code doesn't generally have assert() for mandatory
callbacks/function pointers, probably because the crash is pretty
obvious. Document the methods instead of going into the code.

Make get_tpm_options() mandatory to implement (since all
backend implementation have it).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

backends/tpm.c

@@ -33,7 +33,6 @@ static void tpm_backend_worker_thread(gpointer data, gpointer user_data)
     TPMBackend *s = TPM_BACKEND(user_data);
     TPMBackendClass *k = TPM_BACKEND_GET_CLASS(s);
 
-    assert(k->handle_request != NULL);
     k->handle_request(s, (TPMBackendCmd *)data);
 
     qemu_bh_schedule(s->bh);
@@ -114,8 +113,6 @@ void tpm_backend_cancel_cmd(TPMBackend *s)
 {
     TPMBackendClass *k = TPM_BACKEND_GET_CLASS(s);
 
-    assert(k->cancel_cmd);
-
     k->cancel_cmd(s);
 }
 
@@ -139,8 +136,6 @@ TPMVersion tpm_backend_get_tpm_version(TPMBackend *s)
 {
     TPMBackendClass *k = TPM_BACKEND_GET_CLASS(s);
 
-    assert(k->get_tpm_version);
-
     return k->get_tpm_version(s);
 }
 
@@ -152,9 +147,7 @@ TPMInfo *tpm_backend_query_tpm(TPMBackend *s)
 
     info->id = g_strdup(s->id);
     info->model = tic->model;
-    if (k->get_tpm_options) {
-        info->options = k->get_tpm_options(s);
-    }
+    info->options = k->get_tpm_options(s);
 
     return info;
 }

include/sysemu/tpm_backend.h

@@ -65,15 +65,18 @@ struct TPMBackendClass {
 
     TPMBackend *(*create)(QemuOpts *opts, const char *id);
 
-    /* start up the TPM on the backend */
+    /* start up the TPM on the backend - optional */
     int (*startup_tpm)(TPMBackend *t);
 
+    /* optional */
     void (*reset)(TPMBackend *t);
 
     void (*cancel_cmd)(TPMBackend *t);
 
+    /* optional */
     bool (*get_tpm_established_flag)(TPMBackend *t);
 
+    /* optional */
     int (*reset_tpm_established_flag)(TPMBackend *t, uint8_t locty);
 
     TPMVersion (*get_tpm_version)(TPMBackend *t);