diff --git a/backend.c b/backend.c
index c29968a4..ca1460f8 100644
--- a/backend.c
+++ b/backend.c
@@ -287,8 +287,8 @@ static int sanity_check_all_output_modules(void)
 		}
 
 		/* All modules must provide a data or recv API callback. */
-		if (!outputs[i]->data && !outputs[i]->recv) {
-			sr_err("No data/recv in module %d ('%s').", i, d);
+		if (!outputs[i]->data && !outputs[i]->receive) {
+			sr_err("No data/receive in module %d ('%s').", i, d);
 			errors++;
 		}
 
diff --git a/libsigrok.h b/libsigrok.h
index 73af2d9d..6cda5543 100644
--- a/libsigrok.h
+++ b/libsigrok.h
@@ -454,7 +454,7 @@ struct sr_output_format {
 	 * <code>data_out</code> parameter, so the caller knows not to try
 	 * and g_free() it.
 	 *
-	 * Note: This API call is obsolete, use recv() instead.
+	 * Note: This API call is obsolete, use receive() instead.
 	 *
 	 * @param o Pointer to the respective 'struct sr_output'.
 	 * @param data_in Pointer to the input data buffer.
@@ -486,7 +486,7 @@ struct sr_output_format {
 	 * it stored in the <code>data_out</code> and <code>length_out</code>
 	 * parameters, or NULL if no output was generated.
 	 *
-	 * Note: This API call is obsolete, use recv() instead.
+	 * Note: This API call is obsolete, use receive() instead.
 	 *
 	 * @param o Pointer to the respective 'struct sr_output'.
 	 * @param event_type Type of event that occured.
@@ -496,11 +496,35 @@ struct sr_output_format {
 	 * @return SR_OK upon success, a negative error code otherwise.
 	 */
 	int (*event) (struct sr_output *o, int event_type, uint8_t **data_out,
-		      uint64_t *length_out);
+			uint64_t *length_out);
 
-	GString *(*recv) (struct sr_output *o, const struct sr_dev_inst *sdi,
-			const struct sr_datafeed_packet *packet);
+	/**
+	 * This function is passed a copy of every packed in the data feed.
+	 * Any output generated by the output module in response to the
+	 * packet should be returned in a newly allocated GString
+	 * <code>out</code>, which will be freed by the caller.
+	 *
+	 * Packets not of interest to the output module can just be ignored,
+	 * and the <code>out</code> parameter set to NULL.
+	 *
+	 * @param o Pointer to the respective 'struct sr_output'.
+	 * @param sdi The device instance that generated the packet.
+	 * @param packet The complete packet.
+	 * @param out A pointer where a GString * should be stored if
+	 * the module generates output, or NULL if not.
+	 *
+	 * @return SR_OK upon success, a negative error code otherwise.
+	 */
+	int (*receive) (struct sr_output *o, const struct sr_dev_inst *sdi,
+			const struct sr_datafeed_packet *packet, GString **out);
 
+	/**
+	 * This function is called after the caller is finished using
+	 * the output module, and can be used to free any internal
+	 * resources the module may keep.
+	 *
+	 * @return SR_OK upon success, a negative error code otherwise.
+	 */
 	int (*cleanup) (struct sr_output *o);
 };
 
diff --git a/output/analog.c b/output/analog.c
index 68d1b623..e7e475fc 100644
--- a/output/analog.c
+++ b/output/analog.c
@@ -36,7 +36,6 @@
 struct context {
 	int num_enabled_probes;
 	GPtrArray *probelist;
-	GString *out;
 };
 
 static int init(struct sr_output *o)
@@ -66,8 +65,6 @@ static int init(struct sr_output *o)
 		ctx->num_enabled_probes++;
 	}
 
-	ctx->out = g_string_sized_new(512);
-
 	return SR_OK;
 }
 
@@ -188,10 +185,9 @@ static void fancyprint(int unit, int mqflags, float value, GString *out)
 	g_string_append_c(out, '\n');
 }
 
-static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
-		const struct sr_datafeed_packet *packet)
+static int receive(struct sr_output *o, const struct sr_dev_inst *sdi,
+		const struct sr_datafeed_packet *packet, GString **out)
 {
-	struct context *ctx;
 	const struct sr_datafeed_analog *analog;
 	struct sr_probe *probe;
 	GSList *l;
@@ -200,35 +196,33 @@ static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
 
 	(void)sdi;
 
+	*out = NULL;
 	if (!o || !o->sdi)
-		return NULL;
-	ctx = o->internal;
+		return SR_ERR_ARG;
 
-	g_string_set_size(ctx->out, 0);
 	switch (packet->type) {
-	case SR_DF_HEADER:
-		break;
 	case SR_DF_FRAME_BEGIN:
-		g_string_append_printf(ctx->out, "FRAME-BEGIN\n");
+		*out = g_string_new("FRAME-BEGIN\n");
 		break;
 	case SR_DF_FRAME_END:
-		g_string_append_printf(ctx->out, "FRAME-END\n");
+		*out = g_string_new("FRAME-END\n");
 		break;
 	case SR_DF_ANALOG:
 		analog = packet->payload;
 		fdata = (const float *)analog->data;
+		*out = g_string_sized_new(512);
 		for (i = 0; i < analog->num_samples; i++) {
 			for (l = analog->probes, p = 0; l; l = l->next, p++) {
 				probe = l->data;
-				g_string_append_printf(ctx->out, "%s: ", probe->name);
+				g_string_append_printf(*out, "%s: ", probe->name);
 				fancyprint(analog->unit, analog->mqflags,
-						fdata[i + p], ctx->out);
+						fdata[i + p], *out);
 			}
 		}
 		break;
 	}
 
-	return ctx->out;
+	return SR_OK;
 }
 
 static int cleanup(struct sr_output *o)
@@ -240,7 +234,6 @@ static int cleanup(struct sr_output *o)
 	ctx = o->internal;
 
 	g_ptr_array_free(ctx->probelist, 1);
-	g_string_free(ctx->out, 1);
 	g_free(ctx);
 	o->internal = NULL;
 
@@ -252,6 +245,6 @@ SR_PRIV struct sr_output_format output_analog = {
 	.description = "Analog data",
 	.df_type = SR_DF_ANALOG,
 	.init = init,
-	.recv = receive,
+	.receive = receive,
 	.cleanup = cleanup
 };
diff --git a/output/ols.c b/output/ols.c
index a77dc627..09115f81 100644
--- a/output/ols.c
+++ b/output/ols.c
@@ -41,7 +41,7 @@
 #define sr_err(s, args...) sr_err(DRIVER_LOG_DOMAIN s, ## args)
 
 struct context {
-    uint64_t samplerate;
+	uint64_t samplerate;
 	uint64_t num_samples;
 };
 
@@ -55,7 +55,7 @@ static int init(struct sr_output *o)
 	}
 	o->internal = ctx;
 
-    ctx->samplerate = 0;
+	ctx->samplerate = 0;
 	ctx->num_samples = 0;
 
 	return SR_OK;
@@ -69,7 +69,7 @@ static GString *gen_header(const struct sr_dev_inst *sdi, struct context *ctx)
 	GVariant *gvar;
 	int num_enabled_probes;
 
-    if (!ctx->samplerate && sr_config_get(sdi->driver, SR_CONF_SAMPLERATE,
+	if (!ctx->samplerate && sr_config_get(sdi->driver, SR_CONF_SAMPLERATE,
 			&gvar, sdi) == SR_OK) {
 		ctx->samplerate = g_variant_get_uint64(gvar);
 		g_variant_unref(gvar);
@@ -92,51 +92,50 @@ static GString *gen_header(const struct sr_dev_inst *sdi, struct context *ctx)
 	return s;
 }
 
-static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
-		const struct sr_datafeed_packet *packet)
+static int receive(struct sr_output *o, const struct sr_dev_inst *sdi,
+		const struct sr_datafeed_packet *packet, GString **out)
 {
 	struct context *ctx;
 	const struct sr_datafeed_meta *meta;
 	const struct sr_datafeed_logic *logic;
 	const struct sr_config *src;
 	GSList *l;
-	GString *out;
 	unsigned int i, j;
 	uint8_t c;
 
+	*out = NULL;
 	if (!o || !o->sdi)
-		return NULL;
+		return SR_ERR_ARG;
 	ctx = o->internal;
 
-	out = NULL;
 	switch (packet->type) {
-    case SR_DF_META:
+	case SR_DF_META:
 		meta = packet->payload;
 		for (l = meta->config; l; l = l->next) {
 			src = l->data;
 			if (src->key == SR_CONF_SAMPLERATE)
 				ctx->samplerate = g_variant_get_uint64(src->data);
 		}
-        break;
-    case SR_DF_LOGIC:
+		break;
+	case SR_DF_LOGIC:
 		logic = packet->payload;
 		if (ctx->num_samples == 0) {
 			/* First logic packet in the feed. */
-			out = gen_header(sdi, ctx);
+			*out = gen_header(sdi, ctx);
 		} else
-			out = g_string_sized_new(512);
+			*out = g_string_sized_new(512);
 		for (i = 0; i <= logic->length - logic->unitsize; i += logic->unitsize) {
 			for (j = 0; j < logic->unitsize; j++) {
 				/* The OLS format wants the samples presented MSB first. */
 				c = *((uint8_t *)logic->data + i + logic->unitsize - 1 - j);
-				g_string_append_printf(out, "%02x", c);
+				g_string_append_printf(*out, "%02x", c);
 			}
-			g_string_append_printf(out, "@%"PRIu64"\n", ctx->num_samples++);
+			g_string_append_printf(*out, "@%"PRIu64"\n", ctx->num_samples++);
 		}
 		break;
 	}
 
-    return out;
+	return SR_OK;
 }
 
 static int cleanup(struct sr_output *o)
@@ -147,8 +146,8 @@ static int cleanup(struct sr_output *o)
 		return SR_ERR_ARG;
 
 	ctx = o->internal;
-    g_free(ctx);
-    o->internal = NULL;
+	g_free(ctx);
+	o->internal = NULL;
 
 	return SR_OK;
 }
@@ -158,6 +157,6 @@ SR_PRIV struct sr_output_format output_ols = {
 	.description = "OpenBench Logic Sniffer",
 	.df_type = SR_DF_LOGIC,
 	.init = init,
-	.recv = receive,
+	.receive = receive,
 	.cleanup = cleanup
 };
diff --git a/output/vcd.c b/output/vcd.c
index 90493f05..6e13d704 100644
--- a/output/vcd.c
+++ b/output/vcd.c
@@ -151,12 +151,11 @@ static int init(struct sr_output *o)
 	return SR_OK;
 }
 
-static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
-		const struct sr_datafeed_packet *packet)
+static int receive(struct sr_output *o, const struct sr_dev_inst *sdi,
+		const struct sr_datafeed_packet *packet, GString **out)
 {
 	const struct sr_datafeed_logic *logic;
 	struct context *ctx;
-	GString *text;
 	unsigned int i;
 	int p, curbit, prevbit, index;
 	uint8_t *sample;
@@ -164,23 +163,23 @@ static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
 
 	(void)sdi;
 
+	*out = NULL;
 	if (!o || !o->internal)
-		return NULL;
+		return SR_ERR_ARG;
 	ctx = o->internal;
 
 	if (packet->type == SR_DF_END) {
-		text = g_string_sized_new(16);
-		g_string_printf(text, "$dumpoff\n$end\n");
-		return text;
+		*out = g_string_new("$dumpoff\n$end\n");
+		return SR_OK;
 	} else if (packet->type != SR_DF_LOGIC)
-		return NULL;
+		return SR_OK;
 
 	if (ctx->header) {
 		/* The header is still here, this must be the first packet. */
-		text = ctx->header;
+		*out = ctx->header;
 		ctx->header = NULL;
 	} else {
-		text = g_string_sized_new(512);
+		*out = g_string_sized_new(512);
 	}
 
 	logic = packet->payload;
@@ -199,7 +198,7 @@ static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
 				continue;
 
 			/* Output which signal changed to which value. */
-			g_string_append_printf(text, "#%" PRIu64 "\n%i%c\n",
+			g_string_append_printf(*out, "#%" PRIu64 "\n%i%c\n",
 					(uint64_t)(((float)samplecount / ctx->samplerate)
 					* ctx->period), curbit, (char)('!' + p));
 		}
@@ -207,7 +206,7 @@ static GString *receive(struct sr_output *o, const struct sr_dev_inst *sdi,
 		memcpy(ctx->prevsample, sample, ctx->unitsize);
 	}
 
-	return text;
+	return SR_OK;
 }
 
 static int cleanup(struct sr_output *o)
@@ -228,6 +227,6 @@ struct sr_output_format output_vcd = {
 	.description = "Value Change Dump (VCD)",
 	.df_type = SR_DF_LOGIC,
 	.init = init,
-	.recv = receive,
+	.receive = receive,
 	.cleanup = cleanup,
 };