diff --git a/src/camlib.h b/src/camlib.h
index c350d56..ed820c5 100644
--- a/src/camlib.h
+++ b/src/camlib.h
@@ -129,6 +129,8 @@ struct PtpRuntime {
 	/// @brief For session comm/io structures (holds backend instance pointers)
 	void *comm_backend;
 
+	void *userdata;
+
 	/// @brief Optional (see CAMLIB_DONT_USE_MUTEX)
 	pthread_mutex_t *mutex;
 
diff --git a/src/cl_data.h b/src/cl_data.h
index 0c8df9b..22ad540 100644
--- a/src/cl_data.h
+++ b/src/cl_data.h
@@ -31,10 +31,10 @@ struct PtpDeviceInfo {
 	uint16_t ops_supported[256];
 
 	int events_supported_length;
-	uint16_t events_supported[128];
+	uint16_t events_supported[256];
 
 	int props_supported_length;
-	uint16_t props_supported[128];
+	uint16_t props_supported[256];
 
 	int capture_formats_length;
 	uint16_t capture_formats[32];
@@ -82,7 +82,7 @@ struct PtpObjectInfo {
 
 struct PtpEnumerationForm {
 	uint16_t length;
-	char data[];
+	uint8_t data[];
 };
 
 struct PtpRangeForm {
@@ -169,6 +169,7 @@ int ptp_parse_prop_value(struct PtpRuntime *r);
 int ptp_parse_device_info(struct PtpRuntime *r, struct PtpDeviceInfo *di);
 int ptp_device_info_json(struct PtpDeviceInfo *di, char *buffer, int max);
 int ptp_parse_prop_desc(struct PtpRuntime *r, struct PtpPropDesc *oi);
+int ptp_prop_desc_json(struct PtpPropDesc *pd, char *buffer, int max);
 int ptp_parse_object_info(struct PtpRuntime *r, struct PtpObjectInfo *oi);
 int ptp_storage_info_json(struct PtpStorageInfo *so, char *buffer, int max);
 int ptp_object_info_json(struct PtpObjectInfo *so, char *buffer, int max);
diff --git a/src/data.c b/src/data.c
index 32adcfb..8f40b59 100644
--- a/src/data.c
+++ b/src/data.c
@@ -65,6 +65,7 @@ int ptp_parse_data_u32(void *d, int type, int *out) {
 	case PTP_TC_UINT8:
 		ptp_read_u8(d, &a); (*out) = (int)a; return 1;
 	case PTP_TC_INT16:
+		ptp_read_u16(d, &b); (*out) = (int)((short)b); return 2;
 	case PTP_TC_UINT16:
 		ptp_read_u16(d, &b); (*out) = (int)b; return 2;
 	case PTP_TC_INT32:
@@ -72,6 +73,8 @@ int ptp_parse_data_u32(void *d, int type, int *out) {
 		ptp_read_u32(d, &c); (*out) = (int)c; return 4;
 	}
 
+	// TODO: function to preserve signedness
+
 	// skip the array
 	return ptp_get_data_size(d, type);
 }
@@ -173,6 +176,60 @@ int ptp_parse_prop_desc(struct PtpRuntime *r, struct PtpPropDesc *oi) {
 	return 0;
 }
 
+int ptp_prop_desc_json(struct PtpPropDesc *pd, char *buffer, int max) {
+	int curr = osnprintf(buffer, curr, max, "{\n");
+	curr += osnprintf(buffer, curr, max, "\"code\": %d,\n", pd->code);
+	curr += osnprintf(buffer, curr, max, "\"type\": %d,\n", pd->data_type);
+
+	switch (pd->data_type) {
+		case PTP_TC_INT8:
+		case PTP_TC_UINT8:
+		case PTP_TC_INT16:
+		case PTP_TC_UINT16:
+		case PTP_TC_INT32:
+		case PTP_TC_UINT32:
+		case PTP_TC_INT64:
+		case PTP_TC_UINT64:
+			curr += osnprintf(buffer, curr, max, "\"currentValue32\": %d,\n", pd->current_value32);
+			curr += osnprintf(buffer, curr, max, "\"defaultValue32\": %u,\n", pd->default_value32);
+			break;
+		case PTP_TC_UINT8ARRAY:
+		case PTP_TC_UINT16ARRAY:
+		case PTP_TC_UINT32ARRAY:
+		case PTP_TC_UINT64ARRAY:
+			curr += osnprintf(buffer, curr, max, "\"currentValueArray\": %d,\n", 0);
+			break;
+//		case PTP_TC_STRING:
+	}
+
+	if (pd->form_type == PTP_RangeForm) {
+		curr += osnprintf(buffer, curr, max, "\"validEntries\": [");
+		for (int i = pd->range_form.min; i < pd->range_form.max; i += pd->range_form.step) {
+			char *end = ", ";
+			if (i >= pd->range_form.max - pd->range_form.step) end = "";
+			curr += osnprintf(buffer, curr, max, "%d%s", i, end);
+		}
+		curr += osnprintf(buffer, curr, max, "],\n");
+	} else {
+		curr += osnprintf(buffer, curr, max, "\"validEntries\": [");
+		int of = 0;
+		for (int i = 0; i < pd->enum_form->length; i++) {
+			char *end = ", ";
+			if (i >= pd->enum_form->length - 1) end = "";
+			uint32_t value;
+			void *data = NULL;
+			of += parse_data_data_or_u32(pd->enum_form->data + of, pd->data_type, &value, &data);
+			curr += osnprintf(buffer, curr, max, "%d%s", value, end);
+		}
+		curr += osnprintf(buffer, curr, max, "],\n");
+	}
+
+	curr += osnprintf(buffer, curr, max, "\"form_type\": %d\n", pd->form_type);
+
+	curr += osnprintf(buffer, curr, max, "}");
+	return curr;
+}
+
 int ptp_parse_object_info(struct PtpRuntime *r, struct PtpObjectInfo *oi) {
 	uint8_t *d = ptp_get_payload(r);
 
diff --git a/src/packet.c b/src/packet.c
index e1498ca..ef3a371 100644
--- a/src/packet.c
+++ b/src/packet.c
@@ -63,7 +63,7 @@ int ptp_read_uint16_array_s(uint8_t *bs, uint8_t *be, uint16_t *buf, int max, in
 	boundcheck(bs, be, 4 * n + 4);
 	for (uint32_t i = 0; i < n; i++) {
 		if (i >= max) {
-			ptp_panic("ptp_read_uint16_array overflow\n");
+			ptp_panic("ptp_read_uint16_array overflow %i >= %d\n", i, n);
 		} else {
 			of += ptp_read_u16(bs + of, &buf[i]);
 		}