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drivers: entropy: add driver for VirtIO Entropy device
Add VirtIO Entropy driver. The `virtio,device4` is a somewhat unfamiliar naming convention, but it follows the convention used in Linux. Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>
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‎drivers/entropy/CMakeLists.txt

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@@ -43,6 +43,7 @@ zephyr_library_sources_ifdef(CONFIG_ENTROPY_SMARTBOND_TRNG entropy_smartbon
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zephyr_library_sources_ifdef(CONFIG_ENTROPY_STM32_RNG entropy_stm32.c)
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zephyr_library_sources_ifdef(CONFIG_ENTROPY_SY1XX_TRNG entropy_sy1xx_trng.c)
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zephyr_library_sources_ifdef(CONFIG_ENTROPY_TELINK_B91_TRNG entropy_b91_trng.c)
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zephyr_library_sources_ifdef(CONFIG_ENTROPY_VIRTIO entropy_virtio.c)
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# zephyr-keep-sorted-stop
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zephyr_library_link_libraries_ifdef(CONFIG_BUILD_WITH_TFM tfm_api)

‎drivers/entropy/Kconfig

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@@ -45,6 +45,7 @@ source "drivers/entropy/Kconfig.siwx91x"
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source "drivers/entropy/Kconfig.smartbond"
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source "drivers/entropy/Kconfig.stm32"
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source "drivers/entropy/Kconfig.sy1xx"
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source "drivers/entropy/Kconfig.virtio"
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# zephyr-keep-sorted-stop
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config ENTROPY_HAS_DRIVER

‎drivers/entropy/Kconfig.virtio

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# Copyright (c) 2025 TOKITA Hiroshi
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# SPDX-License-Identifier: Apache-2.0
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config ENTROPY_VIRTIO
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bool "Driver for VirtIO Entropy device"
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depends on DT_HAS_VIRTIO_DEVICE4_ENABLED
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depends on VIRTIO
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select ENTROPY_HAS_DRIVER
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default y
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help
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Enable driver for the VirtIO Entropy device.

‎drivers/entropy/entropy_virtio.c

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/**
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* Copyright (c) 2025 TOKITA Hiroshi
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/drivers/entropy.h>
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#include <zephyr/virtio/virtio.h>
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#include <zephyr/virtio/virtqueue.h>
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#include <zephyr/logging/log.h>
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#define VIRTIO_ENTROPY_QUEUE_IDX 0
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#define DT_DRV_COMPAT virtio_device4
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LOG_MODULE_REGISTER(virtio_entropy, CONFIG_ENTROPY_LOG_LEVEL);
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struct entropy_virtio_config {
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const struct device *vdev;
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};
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struct entropy_virtio_data {
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struct k_sem sem;
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uint32_t received_len;
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};
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static void entropy_virtio_virtq_recv_cb(void *priv, uint32_t len)
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{
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struct entropy_virtio_data *data = priv;
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data->received_len = len;
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k_sem_give(&data->sem);
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}
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static uint16_t entropy_virtio_enum_queues_cb(uint16_t q_index, uint16_t q_size_max, void *unused)
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{
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if (q_index == VIRTIO_ENTROPY_QUEUE_IDX) {
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return MIN(1, q_size_max);
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}
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return 0;
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}
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static int entropy_virtio_get_entropy(const struct device *dev, uint8_t *buffer, uint16_t length)
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{
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struct virtq_buf buf[] = {{.addr = buffer, .len = length}};
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const struct entropy_virtio_config *cfg = dev->config;
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struct entropy_virtio_data *data = dev->data;
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struct virtq *vq = virtio_get_virtqueue(cfg->vdev, VIRTIO_ENTROPY_QUEUE_IDX);
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int ret;
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if (!vq) {
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LOG_ERR("failed to get virtqueue %d", VIRTIO_ENTROPY_QUEUE_IDX);
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return -ENODEV;
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}
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data->received_len = 0;
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ret = virtq_add_buffer_chain(vq, buf, 1, 0, entropy_virtio_virtq_recv_cb, data, K_FOREVER);
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if (ret) {
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LOG_ERR("virtq_add_buffer_chain failed: %d", ret);
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return -EIO;
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}
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virtio_notify_virtqueue(cfg->vdev, VIRTIO_ENTROPY_QUEUE_IDX);
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k_sem_take(&data->sem, K_FOREVER);
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if (data->received_len != length) {
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LOG_ERR("insufficient number of values: %d/%d", data->received_len, length);
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return -EIO;
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}
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return 0;
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}
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static DEVICE_API(entropy, entropy_virtio_api) = {
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.get_entropy = entropy_virtio_get_entropy,
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};
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static int entropy_virtio_init(const struct device *dev)
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{
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const struct entropy_virtio_config *cfg = dev->config;
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struct entropy_virtio_data *data = dev->data;
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int ret;
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ret = virtio_commit_feature_bits(cfg->vdev);
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if (ret != 0) {
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return ret;
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}
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ret = virtio_init_virtqueues(cfg->vdev, 1, entropy_virtio_enum_queues_cb, NULL);
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if (ret) {
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LOG_ERR("virtio_init_virtqueues failed: %d", ret);
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return ret;
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}
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virtio_finalize_init(cfg->vdev);
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k_sem_init(&data->sem, 0, 1);
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LOG_DBG("VirtIO entropy driver initialized");
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return 0;
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}
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#define ENTROPY_VIRTIO_INST(n) \
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static struct entropy_virtio_data entropy_virtio_data_##n; \
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static const struct entropy_virtio_config entropy_virtio_config_##n = { \
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.vdev = DEVICE_DT_GET(DT_PARENT(DT_DRV_INST(n))), \
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}; \
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DEVICE_DT_INST_DEFINE(n, entropy_virtio_init, NULL, &entropy_virtio_data_##n, \
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&entropy_virtio_config_##n, POST_KERNEL, \
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CONFIG_ENTROPY_INIT_PRIORITY, &entropy_virtio_api);
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DT_INST_FOREACH_STATUS_OKAY(ENTROPY_VIRTIO_INST);

‎dts/bindings/rng/virtio,device4.yaml

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# Copyright (c) 2025 TOKITA Hiroshi
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# SPDX-License-Identifier: Apache-2.0
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description: VirtIO Entropy device (ID:4)
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compatible: "virtio,device4"
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include: base.yaml

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