diff --git a/attrib/att-database.h b/attrib/att-database.h
index 3e854aa..e022eec 100644
--- a/attrib/att-database.h
+++ b/attrib/att-database.h
@@ -31,13 +31,13 @@ enum {
 struct attribute {
 	uint16_t handle;
 	bt_uuid_t uuid;
-	int read_reqs;
-	int write_reqs;
+	size_t read_reqs;
+	size_t write_reqs;
 	uint8_t (*read_cb)(struct attribute *a, struct btd_device *device,
 							gpointer user_data);
 	uint8_t (*write_cb)(struct attribute *a, struct btd_device *device,
 							gpointer user_data);
 	gpointer cb_user_data;
-	int len;
+	size_t len;
 	uint8_t *data;
 };
diff --git a/attrib/att.c b/attrib/att.c
index 20a8efa..fc510f4 100644
--- a/attrib/att.c
+++ b/attrib/att.c
@@ -114,9 +114,9 @@ struct att_data_list *att_data_list_alloc(uint16_t num, uint16_t len)
 }
 
 uint16_t enc_read_by_grp_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-							uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
-	const uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end);
+	uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end);
 	uint16_t length;
 
 	if (!uuid)
@@ -141,7 +141,7 @@ uint16_t enc_read_by_grp_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
 	return min_len + length;
 }
 
-uint16_t dec_read_by_grp_req(const uint8_t *pdu, int len, uint16_t *start,
+uint16_t dec_read_by_grp_req(const uint8_t *pdu, size_t len, uint16_t *start,
 						uint16_t *end, bt_uuid_t *uuid)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*start) + sizeof(*end);
@@ -169,7 +169,7 @@ uint16_t dec_read_by_grp_req(const uint8_t *pdu, int len, uint16_t *start,
 }
 
 uint16_t enc_read_by_grp_resp(struct att_data_list *list, uint8_t *pdu,
-								int len)
+								size_t len)
 {
 	int i;
 	uint16_t w;
@@ -178,7 +178,7 @@ uint16_t enc_read_by_grp_resp(struct att_data_list *list, uint8_t *pdu,
 	if (list == NULL)
 		return 0;
 
-	if (len < list->len + 2)
+	if (len < list->len + sizeof(uint8_t) * 2)
 		return 0;
 
 	pdu[0] = ATT_OP_READ_BY_GROUP_RESP;
@@ -195,7 +195,7 @@ uint16_t enc_read_by_grp_resp(struct att_data_list *list, uint8_t *pdu,
 	return w;
 }
 
-struct att_data_list *dec_read_by_grp_resp(const uint8_t *pdu, int len)
+struct att_data_list *dec_read_by_grp_resp(const uint8_t *pdu, size_t len)
 {
 	struct att_data_list *list;
 	const uint8_t *ptr;
@@ -220,7 +220,8 @@ struct att_data_list *dec_read_by_grp_resp(const uint8_t *pdu, int len)
 }
 
 uint16_t enc_find_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-			const uint8_t *value, int vlen, uint8_t *pdu, int len)
+					const uint8_t *value, size_t vlen,
+					uint8_t *pdu, size_t len)
 {
 	uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end) +
 							sizeof(uint16_t);
@@ -253,10 +254,11 @@ uint16_t enc_find_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
 	return min_len;
 }
 
-uint16_t dec_find_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
-		uint16_t *end, bt_uuid_t *uuid, uint8_t *value, int *vlen)
+uint16_t dec_find_by_type_req(const uint8_t *pdu, size_t len, uint16_t *start,
+						uint16_t *end, bt_uuid_t *uuid,
+						uint8_t *value, size_t *vlen)
 {
-	int valuelen;
+	size_t valuelen;
 	uint16_t min_len = sizeof(pdu[0]) + sizeof(*start) +
 						sizeof(*end) + sizeof(uint16_t);
 
@@ -293,7 +295,7 @@ uint16_t dec_find_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
 	return len;
 }
 
-uint16_t enc_find_by_type_resp(GSList *matches, uint8_t *pdu, int len)
+uint16_t enc_find_by_type_resp(GSList *matches, uint8_t *pdu, size_t len)
 {
 	GSList *l;
 	uint16_t offset;
@@ -303,8 +305,9 @@ uint16_t enc_find_by_type_resp(GSList *matches, uint8_t *pdu, int len)
 
 	pdu[0] = ATT_OP_FIND_BY_TYPE_RESP;
 
-	for (l = matches, offset = 1; l && len >= (offset + 4);
-					l = l->next, offset += 4) {
+	for (l = matches, offset = 1;
+				l && len >= (offset + sizeof(uint16_t) * 2);
+				l = l->next, offset += sizeof(uint16_t) * 2) {
 		struct att_range *range = l->data;
 
 		att_put_u16(range->start, &pdu[offset]);
@@ -314,11 +317,11 @@ uint16_t enc_find_by_type_resp(GSList *matches, uint8_t *pdu, int len)
 	return offset;
 }
 
-GSList *dec_find_by_type_resp(const uint8_t *pdu, int len)
+GSList *dec_find_by_type_resp(const uint8_t *pdu, size_t len)
 {
 	struct att_range *range;
 	GSList *matches;
-	int offset;
+	off_t offset;
 
 	if (pdu == NULL || len < 5)
 		return NULL;
@@ -326,7 +329,9 @@ GSList *dec_find_by_type_resp(const uint8_t *pdu, int len)
 	if (pdu[0] != ATT_OP_FIND_BY_TYPE_RESP)
 		return NULL;
 
-	for (offset = 1, matches = NULL; len >= (offset + 4); offset += 4) {
+	for (offset = 1, matches = NULL;
+				len >= (offset + sizeof(uint16_t) * 2);
+				offset += sizeof(uint16_t) * 2) {
 		range = g_new0(struct att_range, 1);
 		range->start = att_get_u16(&pdu[offset]);
 		range->end = att_get_u16(&pdu[offset + 2]);
@@ -338,9 +343,9 @@ GSList *dec_find_by_type_resp(const uint8_t *pdu, int len)
 }
 
 uint16_t enc_read_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-							uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
-	const uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end);
+	uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end);
 	uint16_t length;
 
 	if (!uuid)
@@ -365,7 +370,7 @@ uint16_t enc_read_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
 	return min_len + length;
 }
 
-uint16_t dec_read_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
+uint16_t dec_read_by_type_req(const uint8_t *pdu, size_t len, uint16_t *start,
 						uint16_t *end, bt_uuid_t *uuid)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*start) + sizeof(*end);
@@ -393,10 +398,11 @@ uint16_t dec_read_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
 	return len;
 }
 
-uint16_t enc_read_by_type_resp(struct att_data_list *list, uint8_t *pdu, int len)
+uint16_t enc_read_by_type_resp(struct att_data_list *list, uint8_t *pdu,
+								size_t len)
 {
 	uint8_t *ptr;
-	int i, w, l;
+	size_t i, w, l;
 
 	if (list == NULL)
 		return 0;
@@ -419,7 +425,7 @@ uint16_t enc_read_by_type_resp(struct att_data_list *list, uint8_t *pdu, int len
 	return w;
 }
 
-struct att_data_list *dec_read_by_type_resp(const uint8_t *pdu, int len)
+struct att_data_list *dec_read_by_type_resp(const uint8_t *pdu, size_t len)
 {
 	struct att_data_list *list;
 	const uint8_t *ptr;
@@ -443,8 +449,8 @@ struct att_data_list *dec_read_by_type_resp(const uint8_t *pdu, int len)
 	return list;
 }
 
-uint16_t enc_write_cmd(uint16_t handle, const uint8_t *value, int vlen,
-							uint8_t *pdu, int len)
+uint16_t enc_write_cmd(uint16_t handle, const uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(handle);
 
@@ -468,8 +474,8 @@ uint16_t enc_write_cmd(uint16_t handle, const uint8_t *value, int vlen,
 	return min_len;
 }
 
-uint16_t dec_write_cmd(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int *vlen)
+uint16_t dec_write_cmd(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t *vlen)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*handle);
 
@@ -492,8 +498,8 @@ uint16_t dec_write_cmd(const uint8_t *pdu, int len, uint16_t *handle,
 	return len;
 }
 
-uint16_t enc_write_req(uint16_t handle, const uint8_t *value, int vlen,
-							uint8_t *pdu, int len)
+uint16_t enc_write_req(uint16_t handle, const uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(handle);
 
@@ -517,8 +523,8 @@ uint16_t enc_write_req(uint16_t handle, const uint8_t *value, int vlen,
 	return min_len;
 }
 
-uint16_t dec_write_req(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int *vlen)
+uint16_t dec_write_req(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t *vlen)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*handle);
 
@@ -542,7 +548,7 @@ uint16_t dec_write_req(const uint8_t *pdu, int len, uint16_t *handle,
 	return len;
 }
 
-uint16_t enc_write_resp(uint8_t *pdu, int len)
+uint16_t enc_write_resp(uint8_t *pdu, size_t len)
 {
 	if (pdu == NULL)
 		return 0;
@@ -552,7 +558,7 @@ uint16_t enc_write_resp(uint8_t *pdu, int len)
 	return sizeof(pdu[0]);
 }
 
-uint16_t dec_write_resp(const uint8_t *pdu, int len)
+uint16_t dec_write_resp(const uint8_t *pdu, size_t len)
 {
 	if (pdu == NULL)
 		return 0;
@@ -563,7 +569,7 @@ uint16_t dec_write_resp(const uint8_t *pdu, int len)
 	return len;
 }
 
-uint16_t enc_read_req(uint16_t handle, uint8_t *pdu, int len)
+uint16_t enc_read_req(uint16_t handle, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(handle);
 
@@ -580,7 +586,7 @@ uint16_t enc_read_req(uint16_t handle, uint8_t *pdu, int len)
 }
 
 uint16_t enc_read_blob_req(uint16_t handle, uint16_t offset, uint8_t *pdu,
-									int len)
+									size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(handle) +
 							sizeof(offset);
@@ -598,7 +604,7 @@ uint16_t enc_read_blob_req(uint16_t handle, uint16_t offset, uint8_t *pdu,
 	return min_len;
 }
 
-uint16_t dec_read_req(const uint8_t *pdu, int len, uint16_t *handle)
+uint16_t dec_read_req(const uint8_t *pdu, size_t len, uint16_t *handle)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*handle);
 
@@ -619,7 +625,7 @@ uint16_t dec_read_req(const uint8_t *pdu, int len, uint16_t *handle)
 	return min_len;
 }
 
-uint16_t dec_read_blob_req(const uint8_t *pdu, int len, uint16_t *handle,
+uint16_t dec_read_blob_req(const uint8_t *pdu, size_t len, uint16_t *handle,
 							uint16_t *offset)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*handle) +
@@ -646,7 +652,7 @@ uint16_t dec_read_blob_req(const uint8_t *pdu, int len, uint16_t *handle,
 	return min_len;
 }
 
-uint16_t enc_read_resp(uint8_t *value, int vlen, uint8_t *pdu, int len)
+uint16_t enc_read_resp(uint8_t *value, size_t vlen, uint8_t *pdu, size_t len)
 {
 	if (pdu == NULL)
 		return 0;
@@ -664,8 +670,8 @@ uint16_t enc_read_resp(uint8_t *value, int vlen, uint8_t *pdu, int len)
 	return vlen + 1;
 }
 
-uint16_t enc_read_blob_resp(uint8_t *value, int vlen, uint16_t offset,
-							uint8_t *pdu, int len)
+uint16_t enc_read_blob_resp(uint8_t *value, size_t vlen, uint16_t offset,
+							uint8_t *pdu, size_t len)
 {
 	if (pdu == NULL)
 		return 0;
@@ -681,7 +687,7 @@ uint16_t enc_read_blob_resp(uint8_t *value, int vlen, uint16_t offset,
 	return vlen + 1;
 }
 
-ssize_t dec_read_resp(const uint8_t *pdu, int len, uint8_t *value, int vlen)
+ssize_t dec_read_resp(const uint8_t *pdu, size_t len, uint8_t *value, size_t vlen)
 {
 	if (pdu == NULL)
 		return -EINVAL;
@@ -701,7 +707,7 @@ ssize_t dec_read_resp(const uint8_t *pdu, int len, uint8_t *value, int vlen)
 }
 
 uint16_t enc_error_resp(uint8_t opcode, uint16_t handle, uint8_t status,
-							uint8_t *pdu, int len)
+							uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(opcode) +
 						sizeof(handle) + sizeof(status);
@@ -719,7 +725,7 @@ uint16_t enc_error_resp(uint8_t opcode, uint16_t handle, uint8_t status,
 	return min_len;
 }
 
-uint16_t enc_find_info_req(uint16_t start, uint16_t end, uint8_t *pdu, int len)
+uint16_t enc_find_info_req(uint16_t start, uint16_t end, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(start) + sizeof(end);
 
@@ -736,7 +742,7 @@ uint16_t enc_find_info_req(uint16_t start, uint16_t end, uint8_t *pdu, int len)
 	return min_len;
 }
 
-uint16_t dec_find_info_req(const uint8_t *pdu, int len, uint16_t *start,
+uint16_t dec_find_info_req(const uint8_t *pdu, size_t len, uint16_t *start,
 								uint16_t *end)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*start) + sizeof(*end);
@@ -760,10 +766,10 @@ uint16_t dec_find_info_req(const uint8_t *pdu, int len, uint16_t *start,
 }
 
 uint16_t enc_find_info_resp(uint8_t format, struct att_data_list *list,
-							uint8_t *pdu, int len)
+							uint8_t *pdu, size_t len)
 {
 	uint8_t *ptr;
-	int i, w;
+	size_t i, w;
 
 	if (pdu == NULL)
 		return 0;
@@ -771,7 +777,7 @@ uint16_t enc_find_info_resp(uint8_t format, struct att_data_list *list,
 	if (list == NULL)
 		return 0;
 
-	if (len < list->len + 2)
+	if (len < list->len + sizeof(uint8_t) * 2)
 		return 0;
 
 	pdu[0] = ATT_OP_FIND_INFO_RESP;
@@ -787,7 +793,7 @@ uint16_t enc_find_info_resp(uint8_t format, struct att_data_list *list,
 	return w;
 }
 
-struct att_data_list *dec_find_info_resp(const uint8_t *pdu, int len,
+struct att_data_list *dec_find_info_resp(const uint8_t *pdu, size_t len,
 							uint8_t *format)
 {
 	struct att_data_list *list;
@@ -825,8 +831,8 @@ struct att_data_list *dec_find_info_resp(const uint8_t *pdu, int len,
 	return list;
 }
 
-uint16_t enc_notification(uint16_t handle, uint8_t *value, int vlen,
-						uint8_t *pdu, int len)
+uint16_t enc_notification(uint16_t handle, uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(uint16_t);
 
@@ -843,8 +849,8 @@ uint16_t enc_notification(uint16_t handle, uint8_t *value, int vlen,
 	return vlen + min_len;
 }
 
-uint16_t enc_indication(uint16_t handle, uint8_t *value, int vlen,
-						uint8_t *pdu, int len)
+uint16_t enc_indication(uint16_t handle, uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(uint16_t);
 
@@ -861,8 +867,8 @@ uint16_t enc_indication(uint16_t handle, uint8_t *value, int vlen,
 	return vlen + min_len;
 }
 
-uint16_t dec_indication(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int vlen)
+uint16_t dec_indication(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t vlen)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(uint16_t);
 	uint16_t dlen;
@@ -886,7 +892,7 @@ uint16_t dec_indication(const uint8_t *pdu, int len, uint16_t *handle,
 	return dlen;
 }
 
-uint16_t enc_confirmation(uint8_t *pdu, int len)
+uint16_t enc_confirmation(uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]);
 
@@ -901,7 +907,7 @@ uint16_t enc_confirmation(uint8_t *pdu, int len)
 	return min_len;
 }
 
-uint16_t enc_mtu_req(uint16_t mtu, uint8_t *pdu, int len)
+uint16_t enc_mtu_req(uint16_t mtu, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(mtu);
 
@@ -917,7 +923,7 @@ uint16_t enc_mtu_req(uint16_t mtu, uint8_t *pdu, int len)
 	return min_len;
 }
 
-uint16_t dec_mtu_req(const uint8_t *pdu, int len, uint16_t *mtu)
+uint16_t dec_mtu_req(const uint8_t *pdu, size_t len, uint16_t *mtu)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*mtu);
 
@@ -938,7 +944,7 @@ uint16_t dec_mtu_req(const uint8_t *pdu, int len, uint16_t *mtu)
 	return min_len;
 }
 
-uint16_t enc_mtu_resp(uint16_t mtu, uint8_t *pdu, int len)
+uint16_t enc_mtu_resp(uint16_t mtu, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(mtu);
 
@@ -954,7 +960,7 @@ uint16_t enc_mtu_resp(uint16_t mtu, uint8_t *pdu, int len)
 	return min_len;
 }
 
-uint16_t dec_mtu_resp(const uint8_t *pdu, int len, uint16_t *mtu)
+uint16_t dec_mtu_resp(const uint8_t *pdu, size_t len, uint16_t *mtu)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*mtu);
 
@@ -976,7 +982,7 @@ uint16_t dec_mtu_resp(const uint8_t *pdu, int len, uint16_t *mtu)
 }
 
 uint16_t enc_prep_write_req(uint16_t handle, uint16_t offset,
-			const uint8_t *value, int vlen, uint8_t *pdu, int len)
+			const uint8_t *value, size_t vlen, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(handle) +
 								sizeof(offset);
@@ -1002,8 +1008,8 @@ uint16_t enc_prep_write_req(uint16_t handle, uint16_t offset,
 	return min_len;
 }
 
-uint16_t dec_prep_write_resp(const uint8_t *pdu, int len, uint16_t *handle,
-				uint16_t *offset, uint8_t *value, int *vlen)
+uint16_t dec_prep_write_resp(const uint8_t *pdu, size_t len, uint16_t *handle,
+				uint16_t *offset, uint8_t *value, size_t *vlen)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(*handle) +
 								sizeof(*offset);
@@ -1029,7 +1035,7 @@ uint16_t dec_prep_write_resp(const uint8_t *pdu, int len, uint16_t *handle,
 	return len;
 }
 
-uint16_t enc_exec_write_req(uint8_t flags, uint8_t *pdu, int len)
+uint16_t enc_exec_write_req(uint8_t flags, uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]) + sizeof(flags);
 
@@ -1048,7 +1054,7 @@ uint16_t enc_exec_write_req(uint8_t flags, uint8_t *pdu, int len)
 	return min_len;
 }
 
-uint16_t dec_exec_write_resp(const uint8_t *pdu, int len)
+uint16_t dec_exec_write_resp(const uint8_t *pdu, size_t len)
 {
 	const uint16_t min_len = sizeof(pdu[0]);
 
diff --git a/attrib/att.h b/attrib/att.h
index e7a29cb..9384be5 100644
--- a/attrib/att.h
+++ b/attrib/att.h
@@ -201,69 +201,75 @@ void att_data_list_free(struct att_data_list *list);
 
 const char *att_ecode2str(uint8_t status);
 uint16_t enc_read_by_grp_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-							uint8_t *pdu, int len);
-uint16_t dec_read_by_grp_req(const uint8_t *pdu, int len, uint16_t *start,
-						uint16_t *end, bt_uuid_t *uuid);
-uint16_t enc_read_by_grp_resp(struct att_data_list *list, uint8_t *pdu, int len);
+						uint8_t *pdu, size_t len);
+uint16_t dec_read_by_grp_req(const uint8_t *pdu, size_t len, uint16_t *start,
+					uint16_t *end, bt_uuid_t *uuid);
+uint16_t enc_read_by_grp_resp(struct att_data_list *list, uint8_t *pdu,
+								size_t len);
 uint16_t enc_find_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-			const uint8_t *value, int vlen, uint8_t *pdu, int len);
-uint16_t dec_find_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
-		uint16_t *end, bt_uuid_t *uuid, uint8_t *value, int *vlen);
-uint16_t enc_find_by_type_resp(GSList *ranges, uint8_t *pdu, int len);
-GSList *dec_find_by_type_resp(const uint8_t *pdu, int len);
-struct att_data_list *dec_read_by_grp_resp(const uint8_t *pdu, int len);
+				const uint8_t *value, size_t vlen, uint8_t *pdu,
+				size_t len);
+uint16_t dec_find_by_type_req(const uint8_t *pdu, size_t len, uint16_t *start,
+		uint16_t *end, bt_uuid_t *uuid, uint8_t *value, size_t *vlen);
+uint16_t enc_find_by_type_resp(GSList *ranges, uint8_t *pdu, size_t len);
+GSList *dec_find_by_type_resp(const uint8_t *pdu, size_t len);
+struct att_data_list *dec_read_by_grp_resp(const uint8_t *pdu, size_t len);
 uint16_t enc_read_by_type_req(uint16_t start, uint16_t end, bt_uuid_t *uuid,
-							uint8_t *pdu, int len);
-uint16_t dec_read_by_type_req(const uint8_t *pdu, int len, uint16_t *start,
-						uint16_t *end, bt_uuid_t *uuid);
+						uint8_t *pdu, size_t len);
+uint16_t dec_read_by_type_req(const uint8_t *pdu, size_t len, uint16_t *start,
+					uint16_t *end, bt_uuid_t *uuid);
 uint16_t enc_read_by_type_resp(struct att_data_list *list, uint8_t *pdu,
-								int len);
-uint16_t enc_write_cmd(uint16_t handle, const uint8_t *value, int vlen,
-							uint8_t *pdu, int len);
-uint16_t dec_write_cmd(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int *vlen);
-struct att_data_list *dec_read_by_type_resp(const uint8_t *pdu, int len);
-uint16_t enc_write_req(uint16_t handle, const uint8_t *value, int vlen,
-							uint8_t *pdu, int len);
-uint16_t dec_write_req(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int *vlen);
-uint16_t enc_write_resp(uint8_t *pdu, int len);
-uint16_t dec_write_resp(const uint8_t *pdu, int len);
-uint16_t enc_read_req(uint16_t handle, uint8_t *pdu, int len);
+								size_t len);
+uint16_t enc_write_cmd(uint16_t handle, const uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len);
+uint16_t dec_write_cmd(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t *vlen);
+struct att_data_list *dec_read_by_type_resp(const uint8_t *pdu, size_t len);
+uint16_t enc_write_req(uint16_t handle, const uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len);
+uint16_t dec_write_req(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t *vlen);
+uint16_t enc_write_resp(uint8_t *pdu, size_t len);
+uint16_t dec_write_resp(const uint8_t *pdu, size_t len);
+uint16_t enc_read_req(uint16_t handle, uint8_t *pdu, size_t len);
 uint16_t enc_read_blob_req(uint16_t handle, uint16_t offset, uint8_t *pdu,
-								int len);
-uint16_t dec_read_req(const uint8_t *pdu, int len, uint16_t *handle);
-uint16_t dec_read_blob_req(const uint8_t *pdu, int len, uint16_t *handle,
+								size_t len);
+uint16_t dec_read_req(const uint8_t *pdu, size_t len, uint16_t *handle);
+uint16_t dec_read_blob_req(const uint8_t *pdu, size_t len, uint16_t *handle,
 							uint16_t *offset);
-uint16_t enc_read_resp(uint8_t *value, int vlen, uint8_t *pdu, int len);
-uint16_t enc_read_blob_resp(uint8_t *value, int vlen, uint16_t offset,
-							uint8_t *pdu, int len);
-ssize_t dec_read_resp(const uint8_t *pdu, int len, uint8_t *value, int vlen);
+uint16_t enc_read_resp(uint8_t *value, size_t vlen, uint8_t *pdu, size_t len);
+uint16_t enc_read_blob_resp(uint8_t *value, size_t vlen, uint16_t offset,
+						uint8_t *pdu, size_t len);
+ssize_t dec_read_resp(const uint8_t *pdu, size_t len, uint8_t *value,
+								size_t vlen);
 uint16_t enc_error_resp(uint8_t opcode, uint16_t handle, uint8_t status,
-							uint8_t *pdu, int len);
-uint16_t enc_find_info_req(uint16_t start, uint16_t end, uint8_t *pdu, int len);
-uint16_t dec_find_info_req(const uint8_t *pdu, int len, uint16_t *start,
+						uint8_t *pdu, size_t len);
+uint16_t enc_find_info_req(uint16_t start, uint16_t end, uint8_t *pdu,
+								size_t len);
+uint16_t dec_find_info_req(const uint8_t *pdu, size_t len, uint16_t *start,
 								uint16_t *end);
 uint16_t enc_find_info_resp(uint8_t format, struct att_data_list *list,
-							uint8_t *pdu, int len);
-struct att_data_list *dec_find_info_resp(const uint8_t *pdu, int len,
+						uint8_t *pdu, size_t len);
+struct att_data_list *dec_find_info_resp(const uint8_t *pdu, size_t len,
 							uint8_t *format);
-uint16_t enc_notification(uint16_t handle, uint8_t *value, int vlen,
-						uint8_t *pdu, int len);
-uint16_t enc_indication(uint16_t handle, uint8_t *value, int vlen,
-						uint8_t *pdu, int len);
-uint16_t dec_indication(const uint8_t *pdu, int len, uint16_t *handle,
-						uint8_t *value, int vlen);
-uint16_t enc_confirmation(uint8_t *pdu, int len);
-
-uint16_t enc_mtu_req(uint16_t mtu, uint8_t *pdu, int len);
-uint16_t dec_mtu_req(const uint8_t *pdu, int len, uint16_t *mtu);
-uint16_t enc_mtu_resp(uint16_t mtu, uint8_t *pdu, int len);
-uint16_t dec_mtu_resp(const uint8_t *pdu, int len, uint16_t *mtu);
+uint16_t enc_notification(uint16_t handle, uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len);
+uint16_t enc_indication(uint16_t handle, uint8_t *value, size_t vlen,
+						uint8_t *pdu, size_t len);
+uint16_t dec_indication(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint8_t *value, size_t vlen);
+uint16_t enc_confirmation(uint8_t *pdu, size_t len);
+
+uint16_t enc_mtu_req(uint16_t mtu, uint8_t *pdu, size_t len);
+uint16_t dec_mtu_req(const uint8_t *pdu, size_t len, uint16_t *mtu);
+uint16_t enc_mtu_resp(uint16_t mtu, uint8_t *pdu, size_t len);
+uint16_t dec_mtu_resp(const uint8_t *pdu, size_t len, uint16_t *mtu);
 
 uint16_t enc_prep_write_req(uint16_t handle, uint16_t offset,
-			const uint8_t *value, int vlen, uint8_t *pdu, int len);
-uint16_t dec_prep_write_resp(const uint8_t *pdu, int len, uint16_t *handle,
-				uint16_t *offset, uint8_t *value, int *vlen);
-uint16_t enc_exec_write_req(uint8_t flags, uint8_t *pdu, int len);
-uint16_t dec_exec_write_resp(const uint8_t *pdu, int len);
+					const uint8_t *value, size_t vlen,
+					uint8_t *pdu, size_t len);
+uint16_t dec_prep_write_resp(const uint8_t *pdu, size_t len, uint16_t *handle,
+						uint16_t *offset, uint8_t *value,
+						size_t *vlen);
+uint16_t enc_exec_write_req(uint8_t flags, uint8_t *pdu, size_t len);
+uint16_t dec_exec_write_resp(const uint8_t *pdu, size_t len);
diff --git a/attrib/client.c b/attrib/client.c
index d9c1a2a..c438d7c 100644
--- a/attrib/client.c
+++ b/attrib/client.c
@@ -272,7 +272,7 @@ static void events_handler(const uint8_t *pdu, uint16_t len,
 	uint8_t *opdu;
 	guint handle;
 	uint16_t olen;
-	int plen;
+	size_t plen;
 
 	if (len < 3) {
 		DBG("Malformed notification/indication packet (opcode 0x%02x)",
diff --git a/attrib/gatt.c b/attrib/gatt.c
index b7eb736..9ab283f 100644
--- a/attrib/gatt.c
+++ b/attrib/gatt.c
@@ -84,7 +84,7 @@ static guint16 encode_discover_primary(uint16_t start, uint16_t end,
 		uint16_t u16;
 		uint128_t u128;
 		const void *value;
-		int vlen;
+		size_t vlen;
 
 		/* Discover primary service by service UUID */
 
@@ -114,7 +114,8 @@ static void primary_by_uuid_cb(guint8 status, const guint8 *ipdu,
 	struct att_range *range;
 	uint8_t *buf;
 	guint16 oplen;
-	int err = 0, buflen;
+	int err = 0;
+	size_t buflen;
 
 	if (status) {
 		err = status == ATT_ECODE_ATTR_NOT_FOUND ? 0 : status;
@@ -201,7 +202,7 @@ static void primary_all_cb(guint8 status, const guint8 *ipdu, guint16 iplen,
 	err = 0;
 
 	if (end != 0xffff) {
-		int buflen;
+		size_t buflen;
 		uint8_t *buf = g_attrib_get_buffer(dp->attrib, &buflen);
 		guint16 oplen = encode_discover_primary(end + 1, 0xffff, NULL,
 								buf, buflen);
@@ -221,7 +222,7 @@ guint gatt_discover_primary(GAttrib *attrib, bt_uuid_t *uuid, gatt_cb_t func,
 							gpointer user_data)
 {
 	struct discover_primary *dp;
-	int buflen;
+	size_t buflen;
 	uint8_t *buf = g_attrib_get_buffer(attrib, &buflen);
 	GAttribResultFunc cb;
 	guint16 plen;
@@ -253,7 +254,7 @@ static void char_discovered_cb(guint8 status, const guint8 *ipdu, guint16 iplen,
 	struct discover_char *dc = user_data;
 	struct att_data_list *list;
 	unsigned int i, err;
-	int buflen;
+	size_t buflen;
 	uint8_t *buf;
 	guint16 oplen;
 	bt_uuid_t uuid;
@@ -329,7 +330,7 @@ guint gatt_discover_char(GAttrib *attrib, uint16_t start, uint16_t end,
 						bt_uuid_t *uuid, gatt_cb_t func,
 						gpointer user_data)
 {
-	int buflen;
+	size_t buflen;
 	uint8_t *buf = g_attrib_get_buffer(attrib, &buflen);
 	struct discover_char *dc;
 	bt_uuid_t type_uuid;
@@ -359,7 +360,7 @@ guint gatt_read_char_by_uuid(GAttrib *attrib, uint16_t start, uint16_t end,
 					bt_uuid_t *uuid, GAttribResultFunc func,
 					gpointer user_data)
 {
-	int buflen;
+	size_t buflen;
 	uint8_t *buf = g_attrib_get_buffer(attrib, &buflen);
 	guint16 plen;
 
@@ -400,7 +401,7 @@ static void read_blob_helper(guint8 status, const guint8 *rpdu, guint16 rlen,
 {
 	struct read_long_data *long_read = user_data;
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint8 *tmp;
 	guint16 plen;
 	guint id;
@@ -447,7 +448,7 @@ static void read_char_helper(guint8 status, const guint8 *rpdu,
 					guint16 rlen, gpointer user_data)
 {
 	struct read_long_data *long_read = user_data;
-	int buflen;
+	size_t buflen;
 	uint8_t *buf = g_attrib_get_buffer(long_read->attrib, &buflen);
 	guint16 plen;
 	guint id;
@@ -483,7 +484,7 @@ guint gatt_read_char(GAttrib *attrib, uint16_t handle, uint16_t offset,
 				GAttribResultFunc func, gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 	guint id;
 	struct read_long_data *long_read;
@@ -527,14 +528,14 @@ struct write_long_data {
 	guint16 handle;
 	uint16_t offset;
 	uint8_t *value;
-	int vlen;
+	size_t vlen;
 };
 
 static guint execute_write(GAttrib *attrib, uint8_t flags,
 				GAttribResultFunc func, gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 
 	buf = g_attrib_get_buffer(attrib, &buflen);
@@ -547,7 +548,7 @@ static guint execute_write(GAttrib *attrib, uint8_t flags,
 }
 
 static guint prepare_write(GAttrib *attrib, uint16_t handle, uint16_t offset,
-			uint8_t *value, int vlen, GAttribResultFunc func,
+			uint8_t *value, size_t vlen, GAttribResultFunc func,
 			gpointer user_data);
 
 static void prepare_write_cb(guint8 status, const guint8 *rpdu,
@@ -578,11 +579,11 @@ static void prepare_write_cb(guint8 status, const guint8 *rpdu,
 }
 
 static guint prepare_write(GAttrib *attrib, uint16_t handle, uint16_t offset,
-			uint8_t *value, int vlen, GAttribResultFunc func,
+			uint8_t *value, size_t vlen, GAttribResultFunc func,
 			gpointer user_data)
 {
 	guint16 plen;
-	int buflen;
+	size_t buflen;
 	uint8_t *buf;
 
 	buf = g_attrib_get_buffer(attrib, &buflen);
@@ -597,10 +598,10 @@ static guint prepare_write(GAttrib *attrib, uint16_t handle, uint16_t offset,
 }
 
 guint gatt_write_char(GAttrib *attrib, uint16_t handle, uint8_t *value,
-			int vlen, GAttribResultFunc func, gpointer user_data)
+			size_t vlen, GAttribResultFunc func, gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 	struct write_long_data *long_write;
 
@@ -629,7 +630,7 @@ guint gatt_write_char(GAttrib *attrib, uint16_t handle, uint8_t *value,
 	long_write->func = func;
 	long_write->user_data = user_data;
 	long_write->handle = handle;
-	long_write->value = g_memdup(value,vlen);
+	long_write->value = g_memdup(value, vlen);
 	long_write->vlen = vlen;
 
 	return prepare_write(attrib, handle, long_write->offset, value, vlen,
@@ -640,7 +641,7 @@ guint gatt_exchange_mtu(GAttrib *attrib, uint16_t mtu, GAttribResultFunc func,
 							gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 
 	buf = g_attrib_get_buffer(attrib, &buflen);
@@ -653,7 +654,7 @@ guint gatt_find_info(GAttrib *attrib, uint16_t start, uint16_t end,
 				GAttribResultFunc func, gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 
 	buf = g_attrib_get_buffer(attrib, &buflen);
@@ -669,7 +670,7 @@ guint gatt_write_cmd(GAttrib *attrib, uint16_t handle, uint8_t *value, int vlen,
 				GDestroyNotify notify, gpointer user_data)
 {
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint16 plen;
 
 	buf = g_attrib_get_buffer(attrib, &buflen);
diff --git a/attrib/gatt.h b/attrib/gatt.h
index aab93b6..7690fba 100644
--- a/attrib/gatt.h
+++ b/attrib/gatt.h
@@ -78,7 +78,8 @@ guint gatt_read_char(GAttrib *attrib, uint16_t handle, uint16_t offset,
 				GAttribResultFunc func, gpointer user_data);
 
 guint gatt_write_char(GAttrib *attrib, uint16_t handle, uint8_t *value,
-			int vlen, GAttribResultFunc func, gpointer user_data);
+					size_t vlen, GAttribResultFunc func,
+					gpointer user_data);
 
 guint gatt_find_info(GAttrib *attrib, uint16_t start, uint16_t end,
 				GAttribResultFunc func, gpointer user_data);
diff --git a/attrib/gattrib.c b/attrib/gattrib.c
index 00f59d7..c91f5e9 100644
--- a/attrib/gattrib.c
+++ b/attrib/gattrib.c
@@ -42,7 +42,7 @@ struct _GAttrib {
 	GIOChannel *io;
 	gint refs;
 	uint8_t *buf;
-	int buflen;
+	size_t buflen;
 	guint read_watch;
 	guint write_watch;
 	guint timeout_watch;
@@ -617,7 +617,7 @@ gboolean g_attrib_set_debug(GAttrib *attrib,
 	return TRUE;
 }
 
-uint8_t *g_attrib_get_buffer(GAttrib *attrib, int *len)
+uint8_t *g_attrib_get_buffer(GAttrib *attrib, size_t *len)
 {
 	if (len == NULL)
 		return NULL;
diff --git a/attrib/gattrib.h b/attrib/gattrib.h
index f73b741..bcff039 100644
--- a/attrib/gattrib.h
+++ b/attrib/gattrib.h
@@ -66,7 +66,7 @@ guint g_attrib_register(GAttrib *attrib, guint8 opcode,
 
 gboolean g_attrib_is_encrypted(GAttrib *attrib);
 
-uint8_t *g_attrib_get_buffer(GAttrib *attrib, int *len);
+uint8_t *g_attrib_get_buffer(GAttrib *attrib, size_t *len);
 gboolean g_attrib_set_mtu(GAttrib *attrib, int mtu);
 
 gboolean g_attrib_unregister(GAttrib *attrib, guint id);
diff --git a/attrib/gatttool.c b/attrib/gatttool.c
index a11ca9f..416bb71 100644
--- a/attrib/gatttool.c
+++ b/attrib/gatttool.c
@@ -77,7 +77,7 @@ static void events_handler(const uint8_t *pdu, uint16_t len, gpointer user_data)
 	GAttrib *attrib = user_data;
 	uint8_t *opdu;
 	uint16_t handle, i, olen = 0;
-	int plen;
+	size_t plen;
 
 	handle = att_get_u16(&pdu[1]);
 
diff --git a/attrib/interactive.c b/attrib/interactive.c
index 6cd8bd5..3e8a0d9 100644
--- a/attrib/interactive.c
+++ b/attrib/interactive.c
@@ -103,7 +103,7 @@ static void events_handler(const uint8_t *pdu, uint16_t len, gpointer user_data)
 {
 	uint8_t *opdu;
 	uint16_t handle, i, olen;
-	int plen;
+	size_t plen;
 
 	handle = att_get_u16(&pdu[1]);
 
diff --git a/profiles/thermometer/thermometer.c b/profiles/thermometer/thermometer.c
index 087662e..ad352a9 100644
--- a/profiles/thermometer/thermometer.c
+++ b/profiles/thermometer/thermometer.c
@@ -1142,7 +1142,7 @@ static void ind_handler(const uint8_t *pdu, uint16_t len, gpointer user_data)
 	uint8_t *opdu;
 	uint16_t handle, olen;
 	GSList *l;
-	int plen;
+	size_t plen;
 
 	if (len < 3) {
 		DBG("Bad pdu received");
diff --git a/profiles/time/server.c b/profiles/time/server.c
index d38b9b8..db97056 100644
--- a/profiles/time/server.c
+++ b/profiles/time/server.c
@@ -151,7 +151,7 @@ static uint8_t time_update_control(struct attribute *a,
 	DBG("handle 0x%04x", a->handle);
 
 	if (a->len != 1)
-		DBG("Invalid control point value size: %d", a->len);
+		DBG("Invalid control point value size: %zu", a->len);
 
 	switch (a->data[0]) {
 	case GET_REFERENCE_UPDATE:
diff --git a/src/attrib-server.c b/src/attrib-server.c
index 9064d15..bbed1a9 100644
--- a/src/attrib-server.c
+++ b/src/attrib-server.c
@@ -338,8 +338,9 @@ static uint32_t attrib_create_sdp_new(struct gatt_server *server,
 }
 
 static struct attribute *attrib_db_add_new(struct gatt_server *server,
-				uint16_t handle, bt_uuid_t *uuid, int read_reqs,
-				int write_reqs, const uint8_t *value, int len)
+				uint16_t handle, bt_uuid_t *uuid,
+				size_t read_reqs, size_t write_reqs,
+				const uint8_t *value, size_t len)
 {
 	struct attribute *a;
 	guint h = handle;
@@ -400,7 +401,7 @@ static uint8_t att_check_reqs(struct gatt_channel *channel, uint8_t opcode,
 
 static uint16_t read_by_group(struct gatt_channel *channel, uint16_t start,
 						uint16_t end, bt_uuid_t *uuid,
-						uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
 	struct att_data_list *adl;
 	struct attribute *a;
@@ -516,7 +517,7 @@ static uint16_t read_by_group(struct gatt_channel *channel, uint16_t start,
 
 static uint16_t read_by_type(struct gatt_channel *channel, uint16_t start,
 						uint16_t end, bt_uuid_t *uuid,
-						uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
 	struct att_data_list *adl;
 	GSList *l, *types;
@@ -598,8 +599,8 @@ static uint16_t read_by_type(struct gatt_channel *channel, uint16_t start,
 	return length;
 }
 
-static int find_info(struct gatt_channel *channel, uint16_t start, uint16_t end,
-							uint8_t *pdu, int len)
+static uint16_t find_info(struct gatt_channel *channel, uint16_t start,
+				uint16_t end, uint8_t *pdu, size_t len)
 {
 	struct attribute *a;
 	struct att_data_list *adl;
@@ -673,15 +674,16 @@ static int find_info(struct gatt_channel *channel, uint16_t start, uint16_t end,
 	return length;
 }
 
-static int find_by_type(struct gatt_channel *channel, uint16_t start,
-			uint16_t end, bt_uuid_t *uuid, const uint8_t *value,
-					int vlen, uint8_t *opdu, int mtu)
+static uint16_t find_by_type(struct gatt_channel *channel, uint16_t start,
+				uint16_t end, bt_uuid_t *uuid,
+				const uint8_t *value, size_t vlen,
+				uint8_t *opdu, size_t mtu)
 {
 	struct attribute *a;
 	struct att_range *range;
 	GSList *matches;
 	GList *dl, *database;
-	int len;
+	uint16_t len;
 
 	if (start > end || start == 0x0000)
 		return enc_error_resp(ATT_OP_FIND_BY_TYPE_REQ, start,
@@ -733,7 +735,7 @@ static int find_by_type(struct gatt_channel *channel, uint16_t start,
 }
 
 static uint16_t read_value(struct gatt_channel *channel, uint16_t handle,
-							uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
 	struct attribute *a;
 	uint8_t status;
@@ -774,7 +776,7 @@ static uint16_t read_value(struct gatt_channel *channel, uint16_t handle,
 }
 
 static uint16_t read_blob(struct gatt_channel *channel, uint16_t handle,
-					uint16_t offset, uint8_t *pdu, int len)
+				uint16_t offset, uint8_t *pdu, size_t len)
 {
 	struct attribute *a;
 	uint8_t status;
@@ -820,8 +822,8 @@ static uint16_t read_blob(struct gatt_channel *channel, uint16_t handle,
 }
 
 static uint16_t write_value(struct gatt_channel *channel, uint16_t handle,
-						const uint8_t *value, int vlen,
-						uint8_t *pdu, int len)
+					const uint8_t *value, size_t vlen,
+					uint8_t *pdu, size_t len)
 {
 	struct attribute *a;
 	uint8_t status;
@@ -865,7 +867,7 @@ static uint16_t write_value(struct gatt_channel *channel, uint16_t handle,
 }
 
 static uint16_t mtu_exchange(struct gatt_channel *channel, uint16_t mtu,
-		uint8_t *pdu, int len)
+						uint8_t *pdu, size_t len)
 {
 	GError *gerr = NULL;
 	GIOChannel *io;
@@ -914,7 +916,7 @@ static void channel_handler(const uint8_t *ipdu, uint16_t len,
 	uint16_t length, start, end, mtu, offset;
 	bt_uuid_t uuid;
 	uint8_t status = 0;
-	int vlen;
+	size_t vlen;
 
 	DBG("op 0x%02x", ipdu[0]);
 
@@ -1429,8 +1431,9 @@ uint16_t attrib_db_find_avail(struct btd_adapter *adapter, bt_uuid_t *svc_uuid,
 }
 
 struct attribute *attrib_db_add(struct btd_adapter *adapter, uint16_t handle,
-				bt_uuid_t *uuid, int read_reqs, int write_reqs,
-						const uint8_t *value, int len)
+					bt_uuid_t *uuid, size_t read_reqs,
+					size_t write_reqs,
+					const uint8_t *value, size_t len)
 {
 	GSList *l;
 
@@ -1444,7 +1447,7 @@ struct attribute *attrib_db_add(struct btd_adapter *adapter, uint16_t handle,
 
 int attrib_db_update(struct btd_adapter *adapter, uint16_t handle,
 					bt_uuid_t *uuid, const uint8_t *value,
-					int len, struct attribute **attr)
+					size_t len, struct attribute **attr)
 {
 	struct gatt_server *server;
 	struct attribute *a;
@@ -1513,7 +1516,7 @@ int attrib_db_del(struct btd_adapter *adapter, uint16_t handle)
 }
 
 int attrib_gap_set(struct btd_adapter *adapter, uint16_t uuid,
-						const uint8_t *value, int len)
+					const uint8_t *value, size_t len)
 {
 	struct gatt_server *server;
 	uint16_t handle;
diff --git a/src/attrib-server.h b/src/attrib-server.h
index 7af0cfa..3ec62ed 100644
--- a/src/attrib-server.h
+++ b/src/attrib-server.h
@@ -25,14 +25,15 @@
 uint16_t attrib_db_find_avail(struct btd_adapter *adapter, bt_uuid_t *svc_uuid,
 							uint16_t nitems);
 struct attribute *attrib_db_add(struct btd_adapter *adapter, uint16_t handle,
-				bt_uuid_t *uuid, int read_reqs, int write_reqs,
-				const uint8_t *value, int len);
+				bt_uuid_t *uuid, size_t read_reqs,
+				size_t write_reqs, const uint8_t *value,
+				size_t len);
 int attrib_db_update(struct btd_adapter *adapter, uint16_t handle,
 					bt_uuid_t *uuid, const uint8_t *value,
-					int len, struct attribute **attr);
+					size_t len, struct attribute **attr);
 int attrib_db_del(struct btd_adapter *adapter, uint16_t handle);
 int attrib_gap_set(struct btd_adapter *adapter, uint16_t uuid,
-						const uint8_t *value, int len);
+					const uint8_t *value, size_t len);
 uint32_t attrib_create_sdp(struct btd_adapter *adapter, uint16_t handle,
 							const char *name);
 void attrib_free_sdp(uint32_t sdp_handle);