scpi-pps: Add channel probe facility to scan.

If the number and specs of the device's channels are not static, i.e.
need to be probed, this facility is needed.

Initially this will be used for the Philips PM2800 series, where only
the model returned by *IDN? is needed. However this could also be used
to do actual discovery with vendor-specific SCPI commands.

src/hardware/scpi-pps/api.c

@@ -50,13 +50,15 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
 	struct sr_channel *ch;
 	const struct scpi_pps *device;
 	struct pps_channel *pch;
-	const struct channel_group_spec *cgs;
+	struct channel_spec *channels;
+	struct channel_group_spec *channel_groups, *cgs;
 	struct pps_channel_group *pcg;
 	GRegex *model_re;
 	GMatchInfo *model_mi;
 	GSList *l;
 	uint64_t mask;
-	unsigned int ch_num, ch_idx, i, j;
+	unsigned int num_channels, num_channel_groups, ch_num, ch_idx, i, j;
+	int ret;
 	const char *vendor;
 	char ch_name[16];
 
@@ -90,33 +92,52 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
 	sdi->inst_type = SR_INST_SCPI;
 	sdi->serial_num = g_strdup(hw_info->serial_number);
 
-	sr_scpi_hw_info_free(hw_info);
-	hw_info = NULL;
-
 	devc = g_malloc0(sizeof(struct dev_context));
 	devc->device = device;
 	sdi->priv = devc;
 
+	if (device->num_channels) {
+		/* Static channels and groups. */
+		channels = device->channels;
+		num_channels = device->num_channels;
+		channel_groups = device->channel_groups;
+		num_channel_groups = device->num_channel_groups;
+	} else {
+		/* Channels and groups need to be probed. */
+		ret = device->probe_channels(sdi, hw_info, &channels, &num_channels,
+				&channel_groups, &num_channel_groups);
+		if (ret != SR_OK) {
+			sr_err("Failed to probe for channels.");
+			return NULL;
+		}
+		/*
+		 * Since these were dynamically allocated, we'll need to free them
+		 * later.
+		 */
+		devc->channels = channels;
+		devc->channel_groups = channel_groups;
+	}
+
 	ch_idx = 0;
-	for (ch_num = 0; ch_num < device->num_channels; ch_num++) {
+	for (ch_num = 0; ch_num < num_channels; ch_num++) {
 		/* Create one channel per measurable output unit. */
 		for (i = 0; i < ARRAY_SIZE(pci); i++) {
 			if (!scpi_cmd_get(sdi, pci[i].command))
 				continue;
 			g_snprintf(ch_name, 16, "%s%s", pci[i].prefix,
-					device->channels[ch_num].name);
+					channels[ch_num].name);
 			ch = sr_channel_new(ch_idx++, SR_CHANNEL_ANALOG, TRUE, ch_name);
 			pch = g_malloc0(sizeof(struct pps_channel));
 			pch->hw_output_idx = ch_num;
-			pch->hwname = device->channels[ch_num].name;
+			pch->hwname = channels[ch_num].name;
 			pch->mq = pci[i].mq;
 			ch->priv = pch;
 			sdi->channels = g_slist_append(sdi->channels, ch);
 		}
 	}
 
-	for (i = 0; i < device->num_channel_groups; i++) {
-		cgs = &device->channel_groups[i];
+	for (i = 0; i < num_channel_groups; i++) {
+		cgs = &channel_groups[i];
 		cg = g_malloc0(sizeof(struct sr_channel_group));
 		cg->name = g_strdup(cgs->name);
 		for (j = 0, mask = 1; j < 64; j++, mask <<= 1) {
@@ -135,6 +156,9 @@ static struct sr_dev_inst *probe_device(struct sr_scpi_dev_inst *scpi)
 		sdi->channel_groups = g_slist_append(sdi->channel_groups, cg);
 	}
 
+	sr_scpi_hw_info_free(hw_info);
+	hw_info = NULL;
+
 	scpi_cmd(sdi, SCPI_CMD_LOCAL);
 	sr_scpi_close(scpi);
 
@@ -206,9 +230,19 @@ static int dev_close(struct sr_dev_inst *sdi)
 	return SR_OK;
 }
 
+static void clear_helper(void *priv)
+{
+	struct dev_context *devc;
+
+	devc = priv;
+	g_free(devc->channels);
+	g_free(devc->channel_groups);
+	g_free(devc);
+}
+
 static int cleanup(void)
 {
-	return std_dev_clear(di, NULL);
+	return std_dev_clear(di, clear_helper);
 }
 
 static int config_get(uint32_t key, GVariant **data, const struct sr_dev_inst *sdi,

src/hardware/scpi-pps/protocol.h

@@ -90,6 +90,9 @@ struct scpi_pps {
 	unsigned int num_channel_groups;
 	struct scpi_command *commands;
 	unsigned int num_commands;
+	int (*probe_channels) (struct sr_dev_inst *sdi, struct sr_scpi_hw_info *hwinfo,
+		struct channel_spec **channels, unsigned int *num_channels,
+		struct channel_group_spec **channel_groups, unsigned int *num_channel_groups);
 };
 
 struct channel_spec {
@@ -142,6 +145,8 @@ struct dev_context {
 
 	/* Operational state */
 	gboolean beeper_was_set;
+	struct channel_spec *channels;
+	struct channel_group_spec *channel_groups;
 
 	/* Temporary state across callbacks */
 	struct sr_channel *cur_channel;