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Bluetooth: gatt: avoid assumptions about characteristic handles

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Although the Characteristic Value descriptor is required to be
immediately after the characteristic descriptor, the specification
allows for gaps in the corresponding Attribute handles.  Use the value
handle from the characteristic descriptor for value reads.

See BLUETOOTH CORE SPECIFICATION Version 5.1 Vol 3, Part G section 2.5.1
(p. 2345), first paragraph.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
This commit is contained in:
Peter A. Bigot 2019-06-19 19:22:04 -05:00 • committed by Johan Hedberg
commit 587c35fa64
2 changed files with 39 additions and 7 deletions
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15
include/bluetooth/gatt.h
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@ -245,6 +245,8 @@ struct bt_gatt_include {
struct bt_gatt_chrc {
/** Characteristic UUID. */
const struct bt_uuid *uuid;
/** Characteristic Value handle. */
u16_t value_handle;
/** Characteristic properties. */
u8_t properties;
};
@ -384,6 +386,16 @@ static inline void bt_gatt_foreach_attr(u16_t start_handle, u16_t end_handle,
*/
struct bt_gatt_attr *bt_gatt_attr_next(const struct bt_gatt_attr *attr);
/** @brief Get the handle of the characteristic value descriptor.
*
* @param attr A Characteristic Attribute
*
* @return the handle of the corresponding Characteristic Value. The
* value will be zero (the invalid handle) if @p attr was not a
* characteristic attribute.
*/
uint16_t bt_gatt_attr_value_handle(const struct bt_gatt_attr *attr);
/** @brief Generic Read Attribute value helper.
*
* Read attribute value from local database storing the result into buffer.
@ -536,7 +548,8 @@ ssize_t bt_gatt_attr_read_chrc(struct bt_conn *conn,
BT_GATT_ATTRIBUTE(BT_UUID_GATT_CHRC, BT_GATT_PERM_READ, \
bt_gatt_attr_read_chrc, NULL, \
(&(struct bt_gatt_chrc) { .uuid = _uuid, \
.properties = _props, })), \
.value_handle = 0U, \
.properties = _props, })), \
BT_GATT_ATTRIBUTE(_uuid, _perm, _read, _write, _value)
#define BT_GATT_CCC_MAX (CONFIG_BT_MAX_PAIRED + CONFIG_BT_MAX_CONN)