Bluetooth: Controller: Support FAKE_ENTROPY_NATIVE_POSIX

Add support for use of FAKE_ENTROPY_NATIVE_POSIX as entropy
driver for the Controller on BOARD_NRF54L15BSIM.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>

subsys/bluetooth/controller/Kconfig

@@ -6,7 +6,11 @@
 # The following symbols are enabled depending if the controller actually
 # supports the respective features.
 
+config BT_CTLR_ENTROPY_SUPPORT
+	bool
+
 config BT_CTLR_CRYPTO_SUPPORT
+	depends on BT_CTLR_ENTROPY_SUPPORT
 	bool
 
 config BT_CTLR_LE_ENC_SUPPORT
@@ -147,15 +151,42 @@ config BT_CTLR_HCI
 
 comment "BLE Controller configuration"
 
+config BT_CTLR_ENTROPY
+	bool "Random number generation in Controller"
+	depends on BT_CTLR_ENTROPY_SUPPORT
+	select ENTROPY_GENERATOR
+	default y
+	help
+	  Use random number generation provided by the Controller.
+
+	  Bluetooth Core Specification mandates a use of random number generator
+	  compliant with FIPS PUB 140-2.
+
+	  This option allows for Controller implementation that do not use true
+	  random number generation and hence making the implementation as
+	  experimental.
+
+	  Controller implementations can provide custom bare-metal random number
+	  implementation without any support in Zephyr driver, i.e. there is no
+	  ENTROPY_HAS_DRIVER enabled.
+
 config BT_CTLR_CRYPTO
 	bool "Crypto functions in Controller"
 	depends on BT_CTLR_CRYPTO_SUPPORT
-	select ENTROPY_GENERATOR
 	default y
 	help
 	  Use random number generation and AES encryption support functions
 	  provided by the controller.
 
+	  Support for HCI LE Rand and HCI LE Encrypt commands are mandatory
+	  by Bluetooth Core Specification.
+
+	  In an Application/Host and Controller split (using a HCI transport) or
+	  combined builds for single CPU SoCs, applications can use its own
+	  FIPS-197 compliant cryptographic implementations. In this case the
+	  Controller cryptographic implementations can be disabled to save flash
+	  and RAM usage.
+
 config BT_CTLR_HCI_VS_BUILD_INFO
 	string "Zephyr HCI VS Build Info string"
 	default ""

subsys/bluetooth/controller/Kconfig.ll_sw_split

@@ -11,8 +11,11 @@ config BT_LLL_VENDOR_NORDIC
 	depends on !$(dt_nodelabel_enabled,timer0)
 	depends on !$(dt_nodelabel_enabled,rtc0)
 
-	select ENTROPY_NRF5_RNG if BT_CTLR_CRYPTO
+	select BT_CTLR_ENTROPY_SUPPORT if !SOC_COMPATIBLE_NRF54LX || BOARD_NRF54L15BSIM
+	select FAKE_ENTROPY_NATIVE_POSIX if BT_CTLR_ENTROPY && BOARD_NRF54L15BSIM
+	select ENTROPY_NRF5_RNG if BT_CTLR_ENTROPY && !SOC_COMPATIBLE_NRF54LX
 	select ENTROPY_NRF5_BIAS_CORRECTION if ENTROPY_NRF5_RNG
+	select EXPERIMENTAL if !ENTROPY_HAS_DRIVER || FAKE_ENTROPY_NATIVE_POSIX
 
 	select BT_HAS_HCI_VS
 	select BT_CTLR_CRYPTO_SUPPORT if !SOC_COMPATIBLE_NRF54LX
@@ -69,7 +72,9 @@ config BT_LLL_VENDOR_NORDIC
 config BT_LLL_VENDOR_OPENISA
 	bool "Use OpenISA LLL"
 	depends on SOC_OPENISA_RV32M1
+
 	select BT_HAS_HCI_VS
+	select BT_CTLR_ENTROPY_SUPPORT
 	select BT_CTLR_CRYPTO_SUPPORT
 	select BT_CTLR_LE_ENC_SUPPORT if BT_CTLR_CRYPTO_SUPPORT && \
 					 !BT_CTLR_DATA_LENGTH_CLEAR

subsys/bluetooth/controller/ll_sw/nordic/lll/lll.c

@@ -58,9 +58,9 @@ static struct {
 } event;
 
 /* Entropy device */
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 static const struct device *const dev_entropy = DEVICE_DT_GET(DT_NODELABEL(rng));
-#endif /* CONFIG_ENTROPY_NRF5_RNG */
+#endif /* CONFIG_ENTROPY_HAS_DRIVER */
 
 static int init_reset(void);
 #if defined(CONFIG_BT_CTLR_LOW_LAT_ULL_DONE)
@@ -179,12 +179,12 @@ int lll_init(void)
 {
 	int err;
 
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 	/* Get reference to entropy device */
 	if (!device_is_ready(dev_entropy)) {
 		return -ENODEV;
 	}
-#endif /* CONFIG_ENTROPY_NRF5_RNG */
+#endif /* CONFIG_ENTROPY_HAS_DRIVER */
 
 	/* Initialise LLL internals */
 	event.curr.abort_cb = NULL;
@@ -327,54 +327,54 @@ int lll_deinit(void)
 
 int lll_csrand_get(void *buf, size_t len)
 {
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 	return entropy_get_entropy(dev_entropy, buf, len);
-#else
+#else /* !CONFIG_ENTROPY_HAS_DRIVER */
 	/* FIXME: No suitable entropy device available yet.
 	 *        It is required by Controller to use random numbers.
 	 *        Hence, return uninitialized buf contents, for now.
 	 */
 	return 0;
-#endif
+#endif /* !CONFIG_ENTROPY_HAS_DRIVER */
 }
 
 int lll_csrand_isr_get(void *buf, size_t len)
 {
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 	return entropy_get_entropy_isr(dev_entropy, buf, len, 0);
-#else
+#else /* !CONFIG_ENTROPY_HAS_DRIVER */
 	/* FIXME: No suitable entropy device available yet.
 	 *        It is required by Controller to use random numbers.
 	 *        Hence, return uninitialized buf contents, for now.
 	 */
 	return 0;
-#endif
+#endif /* !CONFIG_ENTROPY_HAS_DRIVER */
 }
 
 int lll_rand_get(void *buf, size_t len)
 {
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 	return entropy_get_entropy(dev_entropy, buf, len);
-#else
+#else /* !CONFIG_ENTROPY_HAS_DRIVER */
 	/* FIXME: No suitable entropy device available yet.
 	 *        It is required by Controller to use random numbers.
 	 *        Hence, return uninitialized buf contents, for now.
 	 */
 	return 0;
-#endif
+#endif /* !CONFIG_ENTROPY_HAS_DRIVER */
 }
 
 int lll_rand_isr_get(void *buf, size_t len)
 {
-#if defined(CONFIG_ENTROPY_NRF5_RNG)
+#if defined(CONFIG_ENTROPY_HAS_DRIVER)
 	return entropy_get_entropy_isr(dev_entropy, buf, len, 0);
-#else
+#else /* !CONFIG_ENTROPY_HAS_DRIVER */
 	/* FIXME: No suitable entropy device available yet.
 	 *        It is required by Controller to use random numbers.
 	 *        Hence, return uninitialized buf contents, for now.
 	 */
 	return 0;
-#endif
+#endif /* !CONFIG_ENTROPY_HAS_DRIVER */
 }
 
 int lll_reset(void)