gatt: Add helper for creating GATT characteristics

This patch adds btd_gatt_add_char() helper. It creates and adds the
Characteristic declaration, and Characteristic value attributes to the
local attribute database.

diff --git a/src/gatt.c b/src/gatt.c
index d3a8062..34f9eea 100644 (file)
--- a/src/gatt.c
+++ b/src/gatt.c
@@ -39,6 +39,9 @@
 static const bt_uuid_t primary_uuid  = { .type = BT_UUID16,
                                        .value.u16 = GATT_PRIM_SVC_UUID };
 
+static const bt_uuid_t chr_uuid = { .type = BT_UUID16,
+                                       .value.u16 = GATT_CHARAC_UUID };
+
 struct btd_attribute {
        uint16_t handle;
        bt_uuid_t type;
@@ -127,6 +130,91 @@ struct btd_attribute *btd_gatt_add_service(const bt_uuid_t *uuid)
        return attr;
 }
 
+struct btd_attribute *btd_gatt_add_char(const bt_uuid_t *uuid,
+                                                       uint8_t properties)
+{
+       struct btd_attribute *char_decl, *char_value = NULL;
+
+       /* Attribute value length */
+       uint16_t len = 1 + 2 + bt_uuid_len(uuid);
+       uint8_t value[len];
+
+       /*
+        * Characteristic DECLARATION
+        *
+        *   TYPE         ATTRIBUTE VALUE
+        * +-------+---------------------------------+
+        * |0x2803 | 0xXX 0xYYYY 0xZZZZ...           |
+        * | (1)   |  (2)   (3)   (4)                |
+        * +------+----------------------------------+
+        * (1) - 2 octets: Characteristic declaration UUID
+        * (2) - 1 octet : Properties
+        * (3) - 2 octets: Handle of the characteristic Value
+        * (4) - 2 or 16 octets: Characteristic UUID
+        */
+
+       value[0] = properties;
+
+       /*
+        * Since we don't know yet the characteristic value attribute
+        * handle, we skip and set it later.
+        */
+
+       put_uuid_le(uuid, &value[3]);
+
+       char_decl = new_const_attribute(&chr_uuid, value, len);
+       if (char_decl == NULL)
+               goto fail;
+
+       char_value = new0(struct btd_attribute, 1);
+       if (char_value == NULL)
+               goto fail;
+
+       if (local_database_add(next_handle, char_decl) < 0)
+               goto fail;
+
+       next_handle = next_handle + 1;
+
+       /*
+        * Characteristic VALUE
+        *
+        *   TYPE         ATTRIBUTE VALUE
+        * +----------+---------------------------------+
+        * |0xZZZZ... | 0x...                           |
+        * |  (1)     |  (2)                            |
+        * +----------+---------------------------------+
+        * (1) - 2 or 16 octets: Characteristic UUID
+        * (2) - N octets: Value is read dynamically from the service
+        * implementation (external entity).
+        */
+
+       char_value->type = *uuid;
+
+       /* TODO: Read & Write callbacks */
+
+       if (local_database_add(next_handle, char_value) < 0)
+               /* TODO: remove declaration */
+               goto fail;
+
+       next_handle = next_handle + 1;
+
+       /*
+        * Update characteristic value handle in characteristic declaration
+        * attribute. For local attributes, we can assume that the handle
+        * representing the characteristic value will get the next available
+        * handle. However, for remote attribute this assumption is not valid.
+        */
+       put_le16(char_value->handle, &char_decl->value[1]);
+
+       return char_value;
+
+fail:
+       free(char_decl);
+       free(char_value);
+
+       return NULL;
+}
+
 void gatt_init(void)
 {
        DBG("Starting GATT server");

diff --git a/src/gatt.h b/src/gatt.h
index 8dd1312..d7acc5b 100644 (file)
--- a/src/gatt.h
+++ b/src/gatt.h
@@ -34,3 +34,15 @@ void gatt_cleanup(void);
  * NULL is returned.
  */
 struct btd_attribute *btd_gatt_add_service(const bt_uuid_t *uuid);
+
+/*
+ * btd_gatt_add_char - Add a characteristic (declaration and value attributes)
+ * to local attribute database.
+ * @uuid:      Characteristic UUID (16-bits or 128-bits).
+ * @properties:        Characteristic properties. See Core SPEC 4.1 page 2183.
+ *
+ * Returns a reference to characteristic value attribute. In case of error,
+ * NULL is returned.
+ */
+struct btd_attribute *btd_gatt_add_char(const bt_uuid_t *uuid,
+                                                       uint8_t properties);