korad-kaxxxxp: rephrase how config setter transmits commands to device

The korad_kaxxxxp_set_value() routine was phrased in redundant and hard
to read ways that were error prone during maintainance. A variables pair
for "command" and "value" variables was assigned to, depending on the
involved parameter of the config setter. And only later in another code
section the text message got combined and was sent to the device. Error
paths which handled unknown keys or non-settable parameters returned
early but had to balance resources on their way out.

This rephrased implementation immediately constructs the text message
when dispatching parameters and looking up their values. Can use more
appropriate printf(3) formats in the respective construction. Emits the
same amount of diagnostics. Releases resources upon exit which were
released during execution. Eliminates dynamic allocation of a 20 byte
buffer.

Tested-By: Pilatomic <[email protected]>

Author: gsigh

src/hardware/korad-kaxxxxp/protocol.c

@@ -167,84 +167,81 @@ static void give_device_time_to_process(struct dev_context *devc)
 SR_PRIV int korad_kaxxxxp_set_value(struct sr_serial_dev_inst *serial,
 				int target, struct dev_context *devc)
 {
-	char *msg;
-	const char *cmd;
-	float value;
+	char msg[20];
 	int ret;
 
 	g_mutex_lock(&devc->rw_mutex);
 	give_device_time_to_process(devc);
 
+	msg[0] = '\0';
+	ret = SR_OK;
 	switch (target) {
 	case KAXXXXP_CURRENT:
 	case KAXXXXP_VOLTAGE:
 	case KAXXXXP_STATUS:
-		sr_err("Can't set measurable parameter %d.", target);
-		g_mutex_unlock(&devc->rw_mutex);
-		return SR_ERR;
+		sr_err("Can't set measured value %d.", target);
+		ret = SR_ERR;
+		break;
 	case KAXXXXP_CURRENT_LIMIT:
-		cmd = "ISET1:%05.3f";
-		value = devc->set_current_limit;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"ISET1:%05.3f", devc->set_current_limit);
 		break;
 	case KAXXXXP_VOLTAGE_TARGET:
-		cmd = "VSET1:%05.2f";
-		value = devc->set_voltage_target;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"VSET1:%05.2f", devc->set_voltage_target);
 		break;
 	case KAXXXXP_OUTPUT:
-		cmd = "OUT%01.0f";
-		value = (devc->set_output_enabled) ? 1 : 0;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"OUT%1d", (devc->set_output_enabled) ? 1 : 0);
 		/* Set value back to recognize changes */
 		devc->output_enabled = devc->set_output_enabled;
 		break;
 	case KAXXXXP_BEEP:
-		cmd = "BEEP%01.0f";
-		value = (devc->set_beep_enabled) ? 1 : 0;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"BEEP%1d", (devc->set_beep_enabled) ? 1 : 0);
 		break;
 	case KAXXXXP_OCP:
-		cmd = "OCP%01.0f";
-		value = (devc->set_ocp_enabled) ? 1 : 0;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"OCP%1d", (devc->set_ocp_enabled) ? 1 : 0);
 		/* Set value back to recognize changes */
 		devc->ocp_enabled = devc->set_ocp_enabled;
 		break;
 	case KAXXXXP_OVP:
-		cmd = "OVP%01.0f";
-		value = (devc->set_ovp_enabled) ? 1 : 0;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"OVP%1d", (devc->set_ovp_enabled) ? 1 : 0);
 		/* Set value back to recognize changes */
 		devc->ovp_enabled = devc->set_ovp_enabled;
 		break;
 	case KAXXXXP_SAVE:
-		cmd = "SAV%01.0f";
 		if (devc->program < 1 || devc->program > 5) {
-			sr_err("Only programs 1-5 supported and %d isn't "
-			       "between them.", devc->program);
-			g_mutex_unlock(&devc->rw_mutex);
-			return SR_ERR;
+			sr_err("Program %d is not in the supported 1-5 range.",
+			       devc->program);
+			ret = SR_ERR;
+			break;
 		}
-		value = devc->program;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"SAV%1d", devc->program);
 		break;
 	case KAXXXXP_RECALL:
-		cmd = "RCL%01.0f";
 		if (devc->program < 1 || devc->program > 5) {
-			sr_err("Only programs 1-5 supported and %d isn't "
-			       "between them.", devc->program);
-			g_mutex_unlock(&devc->rw_mutex);
-			return SR_ERR;
+			sr_err("Program %d is not in the supported 1-5 range.",
+			       devc->program);
+			ret = SR_ERR;
+			break;
 		}
-		value = devc->program;
+		sr_snprintf_ascii(msg, sizeof(msg),
+			"RCL%1d", devc->program);
 		break;
 	default:
-		sr_err("Don't know how to set %d.", target);
-		g_mutex_unlock(&devc->rw_mutex);
-		return SR_ERR;
+		sr_err("Don't know how to set target %d.", target);
+		ret = SR_ERR;
+		break;
 	}
 
-	msg = g_malloc0(20 + 1);
-	if (cmd)
-		sr_snprintf_ascii(msg, 20, cmd, value);
-
-	ret = korad_kaxxxxp_send_cmd(serial, msg);
-	devc->req_sent_at = g_get_monotonic_time();
-	g_free(msg);
+	if (ret == SR_OK && msg[0]) {
+		ret = korad_kaxxxxp_send_cmd(serial, msg);
+		devc->req_sent_at = g_get_monotonic_time();
+	}
 
 	g_mutex_unlock(&devc->rw_mutex);