srd: Support for one or more optional probes.

In the protocol decoder you always get all required probes, then _all_
optional probes in the list of probes in the decode() call.

Example:

 (r1, r2, r3, o1, o2, o3, o4) = pins

In this case r1-r3 are required probes, o1-o4 are optional probes.
However, the value of valid/used/specified probes will be 0 or 1,
whereas the value of probes that were not specified/assigned by the user
will be (at the moment) 42.

The PD can check for a valid probe like this:

  if p in (0, 1):
    ...

Or check for an invalid probe:

  if (p > 1):
    ...

The value of 42 could change to be -1 or None later.

1 files changed, 15 insertions, 0 deletions

diff --git a/decoder.c b/decoder.c
index 4cf4197..6dfeeca 100644
--- a/decoder.c
+++ b/decoder.c
@@ -134,6 +134,8 @@ SRD_API int srd_decoder_load(const char *module_name)
 	struct srd_decoder *d;
 	int alen, ret, i;
 	char **ann;
+	struct srd_probe *p;
+	GSList *l;
 
 	srd_dbg("Loading protocol decoder '%s'.", module_name);
 
@@ -222,6 +224,19 @@ SRD_API int srd_decoder_load(const char *module_name)
 	if (get_probes(d, "optional_probes", &d->opt_probes) != SRD_OK)
 		goto err_out;
 
+	/*
+	 * Fix order numbers for the optional probes.
+	 *
+	 * Example:
+	 * Required probes: r1, r2, r3. Optional: o1, o2, o3, o4.
+	 * 'order' fields in the d->probes list = 0, 1, 2.
+	 * 'order' fields in the d->opt_probes list = 3, 4, 5, 6.
+	 */
+	for (l = d->opt_probes; l; l = l->next) {
+		p = l->data;
+		p->order += g_slist_length(d->probes);
+	}
+
 	/* Store required fields in newly allocated strings. */
 	if (py_attr_as_str(d->py_dec, "id", &(d->id)) != SRD_OK)
 		goto err_out;