bluetooth: services: ras: Implement Ranging Responder role of RAS

Implement the ranging responder (RRSP) server role of the
Ranging Service draft specification.
This allows a ranging requestor (RREQ) to retrieve channel sounding
ranging data from the local device.

This implementation contains support for all mandatory features,
as well as using notifications for data transfer.

Signed-off-by: Aleksandar Stanoev <aleksandar.stanoev@nordicsemi.no>

include/bluetooth/services/ras.h

@@ -11,6 +11,7 @@
 #include <zephyr/kernel.h>
 #include <zephyr/bluetooth/conn.h>
 #include <zephyr/bluetooth/uuid.h>
+#include <zephyr/bluetooth/hci_types.h>
 
 /** @file
  *  @defgroup bt_ras Ranging Service API
@@ -54,7 +55,38 @@ extern "C" {
 #define BT_RAS_RANGING_HEADER_LEN  4
 #define BT_RAS_SUBEVENT_HEADER_LEN 8
 #define BT_RAS_STEP_MODE_LEN       1
-#define BT_RAS_MAX_STEP_DATA_LEN   35
+
+#define BT_RAS_MAX_SUBEVENTS_PER_PROCEDURE 32
+#define BT_RAS_MAX_STEPS_PER_PROCEDURE     256
+
+#define BT_RAS_STEP_MODE_2_3_ANT_DEPENDENT_LEN(antenna_paths)                                      \
+	((antenna_paths + 1) * sizeof(struct bt_hci_le_cs_step_data_tone_info))
+
+#define BT_RAS_STEP_MODE_0_MAX_LEN                                                                 \
+	MAX(sizeof(struct bt_hci_le_cs_step_data_mode_0_initiator),                                \
+	    sizeof(struct bt_hci_le_cs_step_data_mode_0_reflector))
+#define BT_RAS_STEP_MODE_1_MAX_LEN (sizeof(struct bt_hci_le_cs_step_data_mode_1))
+#define BT_RAS_STEP_MODE_2_MAX_LEN                                                                 \
+	(sizeof(struct bt_hci_le_cs_step_data_mode_2) +                                            \
+	 BT_RAS_STEP_MODE_2_3_ANT_DEPENDENT_LEN(CONFIG_BT_RAS_MAX_ANTENNA_PATHS))
+#define BT_RAS_STEP_MODE_3_MAX_LEN                                                                 \
+	(sizeof(struct bt_hci_le_cs_step_data_mode_3) +                                            \
+	 BT_RAS_STEP_MODE_2_3_ANT_DEPENDENT_LEN(CONFIG_BT_RAS_MAX_ANTENNA_PATHS))
+
+#define BT_RAS_STEP_MODE_0_1_MAX_LEN   MAX(BT_RAS_STEP_MODE_0_MAX_LEN, BT_RAS_STEP_MODE_1_MAX_LEN)
+#define BT_RAS_STEP_MODE_0_1_2_MAX_LEN MAX(BT_RAS_STEP_MODE_0_1_MAX_LEN, BT_RAS_STEP_MODE_2_MAX_LEN)
+
+#if defined(CONFIG_BT_RAS_MODE_3_SUPPORTED)
+#define BT_RAS_MAX_STEP_DATA_LEN MAX(BT_RAS_STEP_MODE_0_1_2_MAX_LEN, BT_RAS_STEP_MODE_3_MAX_LEN)
+#else
+#define BT_RAS_MAX_STEP_DATA_LEN BT_RAS_STEP_MODE_0_1_2_MAX_LEN
+#endif
+
+#define BT_RAS_PROCEDURE_MEM                                                                       \
+	(BT_RAS_RANGING_HEADER_LEN +                                                               \
+	 (BT_RAS_MAX_SUBEVENTS_PER_PROCEDURE * BT_RAS_SUBEVENT_HEADER_LEN) +                       \
+	 (BT_RAS_MAX_STEPS_PER_PROCEDURE * BT_RAS_STEP_MODE_LEN) +                                 \
+	 (BT_RAS_MAX_STEPS_PER_PROCEDURE * BT_RAS_MAX_STEP_DATA_LEN))
 
 /** @brief Ranging Header structure as defined in RAS Specification, Table 3.7. */
 struct ras_ranging_header {
@@ -130,6 +162,156 @@ struct ras_subevent_header {
 } __packed;
 BUILD_ASSERT(sizeof(struct ras_subevent_header) == BT_RAS_SUBEVENT_HEADER_LEN);
 
+/** @brief RAS Ranging Data Buffer callback structure. */
+struct bt_ras_rd_buffer_cb {
+	/** @brief New ranging data has been received from the local controller.
+	 *
+	 *  This callback notifies the application that the ranging data buffer
+	 *  has reassembled a complete ranging procedure from the local controller.
+	 *
+	 *  @param conn Connection object.
+	 *  @param ranging_counter Ranging counter of the stored procedure.
+	 */
+	void (*new_ranging_data_received)(struct bt_conn *conn, uint16_t ranging_counter);
+
+	/** @brief Ranging data has been overwritten.
+	 *
+	 *  This callback notifies the application that the ranging data buffer
+	 *  has overwritten a stored procedure due to running out of buffers
+	 *  to store a newer procedure from the local controller.
+	 *
+	 *  @param conn Connection object.
+	 *  @param ranging_counter Ranging counter of the overwritten procedure.
+	 */
+	void (*ranging_data_overwritten)(struct bt_conn *conn, uint16_t ranging_counter);
+
+	sys_snode_t node;
+};
+
+/** @brief RAS Ranging Data buffer structure.
+ *
+ *  Provides storage and metadata to store a complete Ranging Data body
+ *  as defined in RAS Specification, Section 3.2.1.2.
+ *  Buffers can be accessed by the application and RRSP concurrently, and will not
+ *  be overwritten while any references are held via @ref bt_ras_rd_buffer_claim.
+ *
+ *  @note The following CS subevent fields are not included by specification:
+ *        subevent count, step channel, step length.
+ */
+struct ras_rd_buffer {
+	/** Connection with an RRSP instance owning this buffer. */
+	struct bt_conn *conn;
+	/** CS Procedure Ranging Counter stored in this buffer. */
+	uint16_t ranging_counter;
+	/** Write cursor into the procedure subevent buffer. */
+	uint16_t subevent_cursor;
+	/** Reference counter for buffer.
+	 *  The buffer will not be overwritten with active references.
+	 */
+	atomic_t refcount;
+	/** All ranging data has been written, buffer is ready to send. */
+	bool ready;
+	/** Ranging data is being written to this buffer. */
+	bool busy;
+	/** The peer has ACKed this buffer, the overwritten callback will not be called. */
+	bool acked;
+	/** Complete ranging data procedure buffer. */
+	union {
+		uint8_t buf[BT_RAS_PROCEDURE_MEM];
+		struct {
+			struct ras_ranging_header ranging_header;
+			uint8_t subevents[];
+		} __packed;
+	} procedure;
+};
+
+/** @brief Allocate Ranging Responder instance for connection.
+ *
+ *  This will allocate an instance of the Ranging Responder service for the given connection.
+ *
+ *  @note This method must not be called if CONFIG_BT_RAS_RRSP_AUTO_ALLOC_INSTANCE is enabled.
+ *  @note The number of supported instances can be set using CONFIG_BT_RAS_RRSP_MAX_ACTIVE_CONN.
+ *
+ *  @param conn Connection instance.
+ *
+ *  @return Zero in case of success and error code in case of error.
+ */
+int bt_ras_rrsp_alloc(struct bt_conn *conn);
+
+/** @brief Free Ranging Responder instance for connection.
+ *
+ *  This will free an allocated instance of the Ranging Responder service for
+ *  the given connection, if one has been allocated.
+ *  If the connection has no instance allocated, this method has no effect.
+ *
+ *  @note This method must not be called if CONFIG_BT_RAS_RRSP_AUTO_ALLOC_INSTANCE is enabled.
+ *
+ *  @param conn Connection instance.
+ */
+void bt_ras_rrsp_free(struct bt_conn *conn);
+
+/** @brief Register ranging data buffer callbacks.
+ *
+ *  Register callbacks to monitor ranging data buffer state.
+ *
+ *  @param cb Callback struct. Must point to memory that remains valid.
+ */
+void bt_ras_rd_buffer_cb_register(struct bt_ras_rd_buffer_cb *cb);
+
+/** @brief Check if a given ranging counter is available.
+ *
+ *  Checks if the given ranging counter is stored in the buffer and
+ *  has a valid complete ranging data body stored.
+ *
+ *  @param conn Connection instance.
+ *  @param ranging_counter CS procedure ranging counter.
+ *
+ *  @retval true A buffer storing this ranging counter exists and can be claimed.
+ *  @retval false A buffer storing this ranging counter does not exist.
+ */
+bool bt_ras_rd_buffer_ready_check(struct bt_conn *conn, uint16_t ranging_counter);
+
+/** @brief Claim a buffer with a given ranging counter.
+ *
+ *  Returns a pointer to a buffer storing a valid complete ranging data body with
+ *  the requested procedure counter, and increments its reference counter.
+ *
+ *  @param conn Connection instance.
+ *  @param ranging_counter CS procedure ranging counter.
+ *
+ *  @return Pointer to ranging data buffer structure or NULL if no such buffer exists.
+ */
+struct ras_rd_buffer *bt_ras_rd_buffer_claim(struct bt_conn *conn, uint16_t ranging_counter);
+
+/** @brief Release a claimed ranging data buffer.
+ *
+ *  Returns a buffer and decrements its reference counter.
+ *  The buffer will stay available until overwritten by newer ranging data, if
+ *  it has no remaining references.
+ *
+ *  @param buf Pointer to claimed ranging data buffer.
+ *
+ *  @retval 0 Success.
+ *  @retval -EINVAL Invalid buffer provided.
+ */
+int bt_ras_rd_buffer_release(struct ras_rd_buffer *buf);
+
+/** @brief Pull bytes from a ranging data buffer.
+ *
+ *  Utility method to consume up to max_data_len bytes from a buffer.
+ *  The provided read_cursor will be used as the initial offset and updated.
+ *
+ *  @param buf Pointer to claimed ranging data buffer.
+ *  @param out_buf Destination to copy up to max_data_len bytes to.
+ *  @param max_data_len Maximum amount of bytes to copy from the buffer.
+ *  @param read_cursor Current offset into procedure subevent buffer, will be read and written to.
+ *  @param empty Set to true if all data has been read from the ranging data buffer.
+ *
+ *  @return Number of bytes written into out_buf.
+ */
+int bt_ras_rd_buffer_bytes_pull(struct ras_rd_buffer *buf, uint8_t *out_buf, uint16_t max_data_len,
+				uint16_t *read_cursor, bool *empty);
+
 #ifdef __cplusplus
 }
 #endif

subsys/bluetooth/services/ras/Kconfig.ras

@@ -4,10 +4,34 @@
 # SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 #
 
-config BT_RAS
-	bool
+menuconfig BT_RAS
+	bool "Ranging Service [EXPERIMENTAL]"
+	depends on BT_CHANNEL_SOUNDING
+	select BT_NRF_SERVICES
+	select EXPERIMENTAL
 	help
-	  Common Bluetooth GATT Ranging Service modules.
+	  Bluetooth GATT Ranging Service modules - RREQ and RRSP.
+
+if BT_RAS
 
 rsource "rreq/Kconfig.ras_rreq"
 rsource "rrsp/Kconfig.ras_rrsp"
+
+config BT_RAS_MAX_ANTENNA_PATHS
+	int "Maximum number of antenna paths supported"
+	default 4
+	range 1 4
+	help
+	  The number of antenna paths per step that can be stored inside RAS.
+	  Must match the supported CS capabilities of the local device.
+	  This affects the per-instance memory usage of RAS.
+
+config BT_RAS_MODE_3_SUPPORTED
+	bool "Support storing Mode 3 CS steps"
+	default y
+	help
+	  If enabled, RAS will allocate memory for storing Mode 3 CS steps.
+	  Must match the supported CS capabilities of the local device.
+	  This affects the per-instance memory usage of RAS.
+
+endif # BT_RAS

subsys/bluetooth/services/ras/ras_internal.h

@@ -22,6 +22,7 @@ extern "C" {
 #define RASCP_CMD_PARAMS_OFFSET  RASCP_CMD_OPCODE_LEN
 #define RASCP_CMD_PARAMS_MAX_LEN 4
 #define RASCP_WRITE_MAX_LEN      (RASCP_CMD_OPCODE_LEN + RASCP_CMD_PARAMS_MAX_LEN)
+#define RASCP_ACK_DATA_TIMEOUT   K_SECONDS(5)
 
 /** @brief RAS Control Point opcodes as defined in RAS Specification, Table 3.10. */
 enum rascp_opcode {

subsys/bluetooth/services/ras/rreq/Kconfig.ras_rreq

@@ -5,11 +5,8 @@
 #
 
 menuconfig BT_RAS_RREQ
-	bool "Enable GATT Ranging Requester Client [EXPERIMENTAL]"
-	depends on BT_CHANNEL_SOUNDING
+	bool "GATT Ranging Requester Client [EXPERIMENTAL]"
 	select EXPERIMENTAL
-	select BT_NRF_SERVICES
-	select BT_RAS
 
 if BT_RAS_RREQ
 

subsys/bluetooth/services/ras/rrsp/CMakeLists.txt

@@ -6,4 +6,5 @@
 
 zephyr_library_sources_ifdef(
   CONFIG_BT_RAS_RRSP
-  ras_rrsp.c)
+  ras_rrsp.c
+  ras_rd_buffer.c)

subsys/bluetooth/services/ras/rrsp/Kconfig.ras_rrsp

@@ -5,14 +5,29 @@
 #
 
 menuconfig BT_RAS_RRSP
-	bool "Enable GATT Ranging Responder Server [EXPERIMENTAL]"
-	depends on BT_CHANNEL_SOUNDING
+	bool "GATT Ranging Responder Server [EXPERIMENTAL]"
 	select EXPERIMENTAL
-	select BT_NRF_SERVICES
-	select BT_RAS
 
 if BT_RAS_RRSP
 
+config BT_RAS_RRSP_AUTO_ALLOC_INSTANCE
+	bool "Automatically allocate RRSP instances to new connections"
+	default y
+
+config BT_RAS_RRSP_MAX_ACTIVE_CONN
+	int "Number of simultaneously supported RRSP instances"
+	default BT_MAX_CONN
+	range 1 BT_MAX_CONN
+	help
+	  The number of simultaneous connections with an instance of RAS RRSP
+
+config BT_RAS_RRSP_RD_BUFFERS_PER_CONN
+	int "Number of ranging data buffers per connection"
+	default 1
+	range 1 10
+	help
+	  The number of ranging procedures that can be stored inside RRSP.
+
 module = BT_RAS_RRSP
 module-str = RAS_RRSP
 source "${ZEPHYR_BASE}/subsys/logging/Kconfig.template.log_config"