entropy: bt_hci: driver added

Adds an entropy driver that uses Bluetooth HCI commands as its source
of randomness. As this method is blocking, the ISR API is not supported.

As this method will range from relatively slow (same core Bluetooth HCI
controller) to extremely slow (UART HCI Bluetooth controller), use the
xoshiro PRNG by default for RNG generation.

Implements #37186

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

CODEOWNERS

@@ -249,6 +249,7 @@
 /drivers/eeprom/                          @henrikbrixandersen
 /drivers/eeprom/eeprom_stm32.c            @KwonTae-young
 /drivers/entropy/*b91*                    @yurvyn
+/drivers/entropy/*bt_hci*                 @JordanYates
 /drivers/entropy/*rv32m1*                 @dleach02
 /drivers/entropy/*gecko*                  @chrta
 /drivers/entropy/*litex*                  @mateusz-holenko @kgugala @pgielda

drivers/entropy/CMakeLists.txt

@@ -17,3 +17,4 @@ zephyr_library_sources_ifdef(CONFIG_USERSPACE                  entropy_handlers.
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_RV32M1_TRNG        entropy_rv32m1_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_GECKO_TRNG         entropy_gecko_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NEORV32_TRNG       entropy_neorv32_trng.c)
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_BT_HCI             entropy_bt_hci.c)

drivers/entropy/Kconfig

@@ -32,6 +32,7 @@ source "drivers/entropy/Kconfig.rv32m1"
 source "drivers/entropy/Kconfig.litex"
 source "drivers/entropy/Kconfig.gecko"
 source "drivers/entropy/Kconfig.neorv32"
+source "drivers/entropy/Kconfig.bt_hci"
 
 config ENTROPY_HAS_DRIVER
 	bool

drivers/entropy/Kconfig.bt_hci

@@ -0,0 +1,16 @@
+# Copyright (c) 2022, Commonwealth Scientific and Industrial Research
+# Organisation (CSIRO) ABN 41 687 119 230.
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_BT_HCI
+	bool "Bluetooth HCI RNG driver"
+	depends on BT_HCI
+	select ENTROPY_HAS_DRIVER
+	help
+	  Enable Random Number Generator from a Bluetooth HCI device.
+
+# Don't use use Bluetooth HCI as a random source since it will be slow.
+# Instead, use the software implemented xoshiro RNG.
+choice RNG_GENERATOR_CHOICE
+	default XOSHIRO_RANDOM_GENERATOR if ENTROPY_BT_HCI
+endchoice

drivers/entropy/entropy_bt_hci.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2022, Commonwealth Scientific and Industrial Research
+ * Organisation (CSIRO) ABN 41 687 119 230.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT zephyr_bt_hci_entropy
+
+#include <drivers/entropy.h>
+#include <bluetooth/hci.h>
+#include <string.h>
+
+static int entropy_bt_init(const struct device *dev)
+{
+	/* Nothing to do */
+	return 0;
+}
+
+static int entropy_bt_get_entropy(const struct device *dev,
+				  uint8_t *buffer, uint16_t length)
+{
+	struct bt_hci_rp_le_rand *rp;
+	struct net_buf *rsp;
+	int req, ret;
+
+	if (!bt_is_ready()) {
+		return -EAGAIN;
+	}
+
+	while (length > 0) {
+		/* Number of bytes to fill on this iteration */
+		req = MIN(length, sizeof(rp->rand));
+		/* Request the next 8 bytes over HCI */
+		ret = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
+		if (ret) {
+			return ret;
+		}
+		/* Copy random data into buffer */
+		rp = (void *)rsp->data;
+		memcpy(buffer, rp->rand, req);
+		buffer += req;
+		length -= req;
+	}
+	return 0;
+}
+
+/* HCI commands cannot be run from an interrupt context */
+static const struct entropy_driver_api entropy_bt_api = {
+	.get_entropy = entropy_bt_get_entropy,
+	.get_entropy_isr = NULL
+};
+
+#define ENTROPY_BT_HCI_INIT(inst)				  \
+	DEVICE_DT_INST_DEFINE(inst, entropy_bt_init,		  \
+			      NULL, NULL, NULL,			  \
+			      PRE_KERNEL_1,			  \
+			      CONFIG_KERNEL_INIT_PRIORITY_DEVICE, \
+			      &entropy_bt_api);
+
+DT_INST_FOREACH_STATUS_OKAY(ENTROPY_BT_HCI_INIT)

dts/bindings/bluetooth/zephyr,bt-hci-entropy.yaml

@@ -0,0 +1,10 @@
+# Copyright (c) 2018, I-SENSE group of ICCS
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+    Bluetooth module that uses Zephyr's Bluetooth Host Controller Interface as
+    an entropy source
+
+compatible: "zephyr,bt-hci-entropy"
+
+include: base.yaml