[nrf fromtree] bluetooth: host: Add helper function for parsing PCTs

The 12-bit signed values for the results of PBR are a bit
cumbersome, so this adds a helper function to make it easier to work
with the HCI formatted steps.

Signed-off-by: Olivier Lesage <olivier.lesage@nordicsemi.no>
(cherry picked from commit 7e72d46)

Signed-off-by: Sean Madigan <sean.madigan@nordicsemi.no>

include/zephyr/bluetooth/cs.h

@@ -551,6 +551,24 @@ struct bt_le_cs_subevent_step {
 	const uint8_t *data;
 };
 
+/** Sign-extended IQ value extracted from step data. */
+struct bt_le_cs_iq_sample {
+	int16_t i;
+	int16_t q;
+};
+
+/** @brief Extract in-phase and quadrature terms from HCI-formatted PCT.
+ *
+ * Convenience function for processing 24-bit phase correction terms found
+ * in CS step data. The 12-bit signed real and imaginary components are
+ * converted to host endianness and sign-extended.
+ *
+ * @param pct 24-bit little-endian phase correction term.
+ *
+ * @return struct bt_le_cs_iq_sample containing real and imaginary terms as int16_t
+ */
+struct bt_le_cs_iq_sample bt_le_cs_parse_pct(const uint8_t pct[3]);
+
 /** @brief Set all valid channel map bits
  *
  * This command is used to enable all valid channels in a

include/zephyr/bluetooth/hci_types.h

@@ -3607,7 +3607,8 @@ struct bt_hci_evt_le_cs_config_complete {
 
 #define BT_HCI_LE_CS_REF_POWER_LEVEL_UNAVAILABLE 0x7F
 
-#define BT_HCI_LE_CS_PCT_MASK 0xFFF
+#define BT_HCI_LE_CS_PCT_I_MASK 0x000FFF
+#define BT_HCI_LE_CS_PCT_Q_MASK 0xFFF000
 
 #define BT_HCI_LE_CS_TONE_QUALITY_HIGH        0x0
 #define BT_HCI_LE_CS_TONE_QUALITY_MED         0x1

subsys/bluetooth/host/cs.c

@@ -240,6 +240,24 @@ static void reset_reassembly_results(void)
 	memset(&reassembled_result, 0, sizeof(struct bt_conn_le_cs_subevent_result));
 }
 
+/** @brief Converts PCT to a pair of int16_t
+ *
+ */
+struct bt_le_cs_iq_sample bt_le_cs_parse_pct(const uint8_t pct[3])
+{
+	uint32_t pct_u32 = sys_get_le24(pct);
+
+	/* Extract I and Q. */
+	uint16_t i_u16 = pct_u32 & BT_HCI_LE_CS_PCT_I_MASK;
+	uint16_t q_u16 = (pct_u32 & BT_HCI_LE_CS_PCT_Q_MASK) >> 12;
+
+	/* Convert from 12-bit 2's complement to int16_t */
+	int16_t i = (i_u16 ^ BIT(11)) - BIT(11);
+	int16_t q = (q_u16 ^ BIT(11)) - BIT(11);
+
+	return (struct bt_le_cs_iq_sample){.i = i, .q = q};
+}
+
 void bt_le_cs_set_valid_chmap_bits(uint8_t channel_map[10])
 {
 	memset(channel_map, 0xFF, 10);

tests/bluetooth/host/cs/bt_le_cs_parse_pct/CMakeLists.txt

@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr COMPONENTS unittest REQUIRED HINTS $ENV{ZEPHYR_BASE})
+
+project(bt_step_data_parse)
+
+include_directories(BEFORE
+    ${ZEPHYR_BASE}/tests/bluetooth/host/cs/mocks
+)
+
+add_subdirectory(${ZEPHYR_BASE}/tests/bluetooth/host host_mocks)
+add_subdirectory(${ZEPHYR_BASE}/tests/bluetooth/host/cs/mocks mocks)
+
+target_link_libraries(testbinary PRIVATE mocks host_mocks)
+
+target_sources(testbinary
+    PRIVATE
+    src/main.c
+
+    ${ZEPHYR_BASE}/subsys/bluetooth/host/cs.c
+    ${ZEPHYR_BASE}/lib/net_buf/buf_simple.c
+    ${ZEPHYR_BASE}/subsys/logging/log_minimal.c
+)

tests/bluetooth/host/cs/bt_le_cs_parse_pct/prj.conf

@@ -0,0 +1,10 @@
+CONFIG_ZTEST=y
+CONFIG_BT=y
+CONFIG_BT_HCI=y
+CONFIG_BT_CENTRAL=y
+CONFIG_BT_CHANNEL_SOUNDING=y
+CONFIG_ASSERT=y
+CONFIG_ASSERT_LEVEL=2
+CONFIG_ASSERT_VERBOSE=y
+CONFIG_ASSERT_ON_ERRORS=y
+CONFIG_NET_BUF=y

tests/bluetooth/host/cs/bt_le_cs_parse_pct/src/main.c

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/bluetooth/cs.h>
+#include <zephyr/fff.h>
+
+DEFINE_FFF_GLOBALS;
+
+ZTEST_SUITE(bt_le_cs_parse_pct, NULL, NULL, NULL, NULL, NULL);
+
+/*
+ *  Test success case
+ *
+ *  Constraints:
+ *   - Valid PCT is passed in
+ *
+ *  Expected behaviour:
+ *   - IQ term matches expected values
+ */
+ZTEST(bt_le_cs_parse_pct, test_parsing_success)
+{
+	struct bt_le_cs_iq_sample iq;
+
+	struct {
+		uint8_t input[3];
+		struct bt_le_cs_iq_sample output;
+	} test_vector[] = {
+		/* Edge cases */
+		{.input = {0x00, 0x00, 0x00}, .output = {.i = 0, .q = 0}},
+		{.input = {0xFF, 0xFF, 0xFF}, .output = {.i = -1, .q = -1}},
+		{.input = {0xFF, 0x00, 0xFF}, .output = {.i = 255, .q = -16}},
+		{.input = {0xFF, 0x00, 0x00}, .output = {.i = 255, .q = 0}},
+		{.input = {0x00, 0xFF, 0x00}, .output = {.i = -256, .q = 15}},
+		{.input = {0x00, 0x00, 0xFF}, .output = {.i = 0, .q = -16}},
+		{.input = {0x00, 0x08, 0x80}, .output = {.i = -2048, .q = -2048}},
+		{.input = {0xFF, 0xF7, 0x7F}, .output = {.i = 2047, .q = 2047}},
+
+		/* Randomly generated using python */
+		{.input = {0xEF, 0xCD, 0xAB}, .output = {.i = -529, .q = -1348}},
+		{.input = {0x30, 0x75, 0x44}, .output = {.i = 1328, .q = 1095}},
+		{.input = {0x46, 0x5D, 0xEB}, .output = {.i = -698, .q = -331}},
+		{.input = {0xE8, 0x14, 0x45}, .output = {.i = 1256, .q = 1105}},
+		{.input = {0x23, 0xCA, 0x5C}, .output = {.i = -1501, .q = 1484}},
+		{.input = {0x68, 0xA0, 0x15}, .output = {.i = 104, .q = 346}},
+		{.input = {0x39, 0x73, 0x1B}, .output = {.i = 825, .q = 439}},
+		{.input = {0x23, 0x72, 0x3D}, .output = {.i = 547, .q = 983}},
+		{.input = {0xF5, 0xF8, 0x3D}, .output = {.i = -1803, .q = 991}},
+		{.input = {0xF7, 0xB4, 0xB9}, .output = {.i = 1271, .q = -1125}},
+		{.input = {0x61, 0x9F, 0xD5}, .output = {.i = -159, .q = -679}},
+		{.input = {0x9B, 0x21, 0xC6}, .output = {.i = 411, .q = -926}},
+		{.input = {0x14, 0x86, 0x0F}, .output = {.i = 1556, .q = 248}},
+		{.input = {0x8E, 0xBB, 0xC6}, .output = {.i = -1138, .q = -917}},
+		{.input = {0x5B, 0xD1, 0xC2}, .output = {.i = 347, .q = -979}},
+		{.input = {0x99, 0x4A, 0x28}, .output = {.i = -1383, .q = 644}},
+		{.input = {0x32, 0x16, 0x2B}, .output = {.i = 1586, .q = 689}},
+		{.input = {0x3E, 0x8C, 0xD4}, .output = {.i = -962, .q = -696}},
+		{.input = {0x2B, 0x1F, 0x95}, .output = {.i = -213, .q = -1711}},
+		{.input = {0x22, 0xE6, 0xD6}, .output = {.i = 1570, .q = -658}},
+		{.input = {0x0B, 0x31, 0xD6}, .output = {.i = 267, .q = -669}},
+		{.input = {0x1B, 0x98, 0x9D}, .output = {.i = -2021, .q = -1575}},
+		{.input = {0x8E, 0x97, 0x63}, .output = {.i = 1934, .q = 1593}},
+		{.input = {0x97, 0x91, 0x8D}, .output = {.i = 407, .q = -1831}},
+		{.input = {0x67, 0xF7, 0x1F}, .output = {.i = 1895, .q = 511}},
+		{.input = {0xD6, 0x5C, 0x23}, .output = {.i = -810, .q = 565}},
+		{.input = {0x92, 0xD3, 0x0B}, .output = {.i = 914, .q = 189}},
+		{.input = {0xE8, 0xF3, 0x23}, .output = {.i = 1000, .q = 575}},
+		{.input = {0xE6, 0xE3, 0xAD}, .output = {.i = 998, .q = -1314}},
+		{.input = {0x6E, 0x70, 0xA9}, .output = {.i = 110, .q = -1385}},
+		{.input = {0x63, 0x65, 0x28}, .output = {.i = 1379, .q = 646}},
+		{.input = {0x27, 0x0F, 0x32}, .output = {.i = -217, .q = 800}},
+		{.input = {0x3F, 0x8C, 0xE1}, .output = {.i = -961, .q = -488}},
+		{.input = {0x4E, 0x86, 0xAA}, .output = {.i = 1614, .q = -1368}},
+		{.input = {0x9E, 0xD1, 0xF6}, .output = {.i = 414, .q = -147}},
+		{.input = {0x86, 0x09, 0x56}, .output = {.i = -1658, .q = 1376}},
+		{.input = {0xFF, 0x09, 0x41}, .output = {.i = -1537, .q = 1040}},
+		{.input = {0x89, 0xC5, 0x1F}, .output = {.i = 1417, .q = 508}},
+		{.input = {0x1A, 0xE2, 0x9A}, .output = {.i = 538, .q = -1618}},
+		{.input = {0x7E, 0x03, 0xB8}, .output = {.i = 894, .q = -1152}},
+		{.input = {0x5E, 0x28, 0xB3}, .output = {.i = -1954, .q = -1230}},
+		{.input = {0xFF, 0x50, 0xF0}, .output = {.i = 255, .q = -251}},
+		{.input = {0xB0, 0x07, 0x87}, .output = {.i = 1968, .q = -1936}},
+		{.input = {0x7E, 0xD7, 0x0C}, .output = {.i = 1918, .q = 205}},
+		{.input = {0x26, 0xA2, 0xC9}, .output = {.i = 550, .q = -870}},
+		{.input = {0x97, 0x71, 0x72}, .output = {.i = 407, .q = 1831}},
+		{.input = {0x73, 0x0E, 0xC1}, .output = {.i = -397, .q = -1008}},
+		{.input = {0xAC, 0x20, 0x6B}, .output = {.i = 172, .q = 1714}},
+		{.input = {0x85, 0x7D, 0xB4}, .output = {.i = -635, .q = -1209}},
+		{.input = {0xCC, 0xE3, 0x1B}, .output = {.i = 972, .q = 446}},
+		{.input = {0x88, 0x48, 0x65}, .output = {.i = -1912, .q = 1620}},
+	};
+
+	for (uint16_t k = 0; k < ARRAY_SIZE(test_vector); k++) {
+		iq = bt_le_cs_parse_pct(test_vector[k].input);
+
+		zassert_equal(iq.i, test_vector[k].output.i,
+			      "Failed for k = %u, expected %d, not %d", k, test_vector[k].output.i,
+			      iq.i);
+		zassert_equal(iq.q, test_vector[k].output.q,
+			      "Failed for k = %u, expected %d, not %d", k, test_vector[k].output.q,
+			      iq.q);
+	}
+}

tests/bluetooth/host/cs/bt_le_cs_parse_pct/testcase.yaml

@@ -0,0 +1,7 @@
+common:
+  tags:
+    - bluetooth
+    - host
+tests:
+  bluetooth.host.cs.bt_le_cs_parse_pct:
+    type: unit