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Bluetooth: Host: Update API docs on GATT request failures

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Document the deadlock avoidance in ATT request queueing.

Add more precise description of the callback and how long the argument
must be kept valid for.

Signed-off-by: Aleksander Wasaznik <aleksander.wasaznik@nordicsemi.no>
This commit is contained in:
Aleksander Wasaznik 2021-11-22 13:42:31 +01:00 committed by Carles Cufí
parent 30098c881f
commit c65bb791bf
1 changed files with 97 additions and 17 deletions
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114
include/bluetooth/gatt.h
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@ -1216,10 +1216,22 @@ struct bt_gatt_exchange_params {
*
* @note Shall only be used once per connection.
*
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread. @p params must remain valid until start of callback.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param params Exchange MTU parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->func on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_exchange_mtu(struct bt_conn *conn,
struct bt_gatt_exchange_params *params);
@ -1348,13 +1360,23 @@ struct bt_gatt_discover_params {
* For each attribute found the callback is called which can then decide
* whether to continue discovering or stop.
*
* @note This procedure is asynchronous therefore the parameters need to
* remains valid while it is active.
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread. @p params must remain valid until start of callback where
* iter `attr` is `NULL` or callback will return `BT_GATT_ITER_STOP`.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param params Discover parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->func on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_discover(struct bt_conn *conn,
struct bt_gatt_discover_params *params);
@ -1433,13 +1455,22 @@ struct bt_gatt_read_params {
* caller will need to read the remaining data separately using the handle and
* offset.
*
* @note This procedure is asynchronous therefore the parameters need to
* remains valid while it is active.
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread. @p params must remain valid until start of callback.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param params Read parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->func on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_read(struct bt_conn *conn, struct bt_gatt_read_params *params);
@ -1471,16 +1502,24 @@ struct bt_gatt_write_params {
/** @brief Write Attribute Value by handle
*
* This procedure write the attribute value and return the result in the
* callback.
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread. @p params must remain valid until start of callback.
*
* @note This procedure is asynchronous therefore the parameters need to
* remains valid while it is active.
* This function will block while the ATT request queue is full, except when
* called from Bluetooth event context. When called from Bluetooth context,
* this function will instead instead return `-ENOMEM` if it would block to
* avoid a deadlock.
*
* @param conn Connection object.
* @param params Write parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->func on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside Bluetooth event context to get blocking behavior. Queue size is
* controlled by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_write(struct bt_conn *conn, struct bt_gatt_write_params *params);
@ -1495,13 +1534,15 @@ int bt_gatt_write(struct bt_conn *conn, struct bt_gatt_write_params *params);
* resources for the callback but instead return an error.
* The number of pending callbacks can be increased with the
* @kconfig{CONFIG_BT_CONN_TX_MAX} option.
*
* @note By using a callback it also disable the internal flow control
* which would prevent sending multiple commands without waiting for
* their transmissions to complete, so if that is required the caller
* shall not submit more data until the callback is called.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param handle Attribute handle.
* @param data Data to be written.
@ -1510,7 +1551,12 @@ int bt_gatt_write(struct bt_conn *conn, struct bt_gatt_write_params *params);
* @param func Transmission complete callback.
* @param user_data User data to be passed back to callback.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_write_without_response_cb(struct bt_conn *conn, uint16_t handle,
const void *data, uint16_t length,
@ -1522,13 +1568,21 @@ int bt_gatt_write_without_response_cb(struct bt_conn *conn, uint16_t handle,
* This procedure write the attribute value without requiring an
* acknowledgment that the write was successfully performed
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param handle Attribute handle.
* @param data Data to be written.
* @param length Data length.
* @param sign Whether to sign data
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
static inline int bt_gatt_write_without_response(struct bt_conn *conn,
uint16_t handle, const void *data,
@ -1630,13 +1684,27 @@ struct bt_gatt_subscribe_params {
* this callback. Notification callback with NULL data will not be called if
* subscription was removed by this method.
*
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread. @p params must remain valid until start of callback.
* The Notification callback @p params->notify is also called from the BT RX
* thread.
*
* @note Notifications are asynchronous therefore the parameters need to
* remain valid while subscribed.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param params Subscribe parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->write on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_subscribe(struct bt_conn *conn,
struct bt_gatt_subscribe_params *params);
@ -1667,10 +1735,22 @@ int bt_gatt_resubscribe(uint8_t id, const bt_addr_le_t *peer,
* will be called if subscription was removed by this call, until then the
* parameters cannot be reused.
*
* The Response comes in callback @p params->func. The callback is run from
* the BT RX thread.
*
* This function will block while the ATT request queue is full, except when
* called from the BT RX thread, as this would cause a deadlock.
*
* @param conn Connection object.
* @param params Subscribe parameters.
*
* @return 0 in case of success or negative value in case of error.
* @retval 0 Successfully queued request. Will call @p params->write on
* resolution.
*
* @retval -ENOMEM ATT request queue is full and blocking would cause deadlock.
* Allow a pending request to resolve before retrying, or call this function
* outside the BT RX thread to get blocking behavior. Queue size is controlled
* by @kconfig{CONFIG_BT_L2CAP_TX_BUF_COUNT}.
*/
int bt_gatt_unsubscribe(struct bt_conn *conn,
struct bt_gatt_subscribe_params *params);