serial: add an uart-bridge driver
Add a reusable uart-bridge driver that echoes data between two serial devices. It's mainly meant to be used with one of the devices being an USB CDC-ACM, the data is buffered, there's a pause feature to stop the USB endpoint when the hardware UART is filling up to avoid overrun and there's a helper function used to propagate the USB uart configuration to the hardware one. Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
This commit is contained in:
Fabio Baltieri
Fabio Baltieri
parent
6e9cfcdcd5
commit
3cb8f745a6
@ -23,6 +23,7 @@ zephyr_library_sources_ifdef(CONFIG_UART_ALTERA_JTAG uart_altera_jtag.c)
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zephyr_library_sources_ifdef(CONFIG_UART_APBUART uart_apbuart.c)
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zephyr_library_sources_ifdef(CONFIG_UART_BCM2711_MU uart_bcm2711.c)
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zephyr_library_sources_ifdef(CONFIG_UART_BFLB uart_bflb.c)
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zephyr_library_sources_ifdef(CONFIG_UART_BRIDGE uart_bridge.c)
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zephyr_library_sources_ifdef(CONFIG_UART_BT uart_bt.c)
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zephyr_library_sources_ifdef(CONFIG_UART_CC13XX_CC26XX uart_cc13xx_cc26xx.c)
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zephyr_library_sources_ifdef(CONFIG_UART_CC23X0 uart_cc23x0.c)
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@ -164,6 +164,7 @@ rsource "Kconfig.apbuart"
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rsource "Kconfig.b91"
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rsource "Kconfig.bcm2711"
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rsource "Kconfig.bflb"
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rsource "Kconfig.bridge"
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rsource "Kconfig.bt"
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rsource "Kconfig.cc13xx_cc26xx"
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rsource "Kconfig.cc23x0"
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18
drivers/serial/Kconfig.bridge
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18
drivers/serial/Kconfig.bridge
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@ -0,0 +1,18 @@
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# Copyright 2025 Google LLC
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# SPDX-License-Identifier: Apache-2.0
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config UART_BRIDGE
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bool "UART bridge"
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default y
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depends on DT_HAS_ZEPHYR_UART_BRIDGE_ENABLED
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select UART_INTERRUPT_DRIVEN
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select RING_BUFFER
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help
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Enable the UART bridge driver.
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config UART_BRIDGE_BUF_SIZE
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int "UART bridge buffer size"
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default 256
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depends on UART_BRIDGE
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help
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Size of the bridge ring buffers in bytes.
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229
drivers/serial/uart_bridge.c
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229
drivers/serial/uart_bridge.c
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@ -0,0 +1,229 @@
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/*
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* Copyright 2025 Google LLC
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/device.h>
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#include <zephyr/drivers/uart.h>
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#include <zephyr/kernel.h>
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#include <zephyr/logging/log.h>
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#include <zephyr/sys/ring_buffer.h>
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#include <zephyr/drivers/uart/uart_bridge.h>
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#define DT_DRV_COMPAT zephyr_uart_bridge
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LOG_MODULE_REGISTER(uart_bridge, LOG_LEVEL_INF);
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#define RING_BUF_SIZE CONFIG_UART_BRIDGE_BUF_SIZE
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#define RING_BUF_FULL_THRESHOLD (RING_BUF_SIZE / 3)
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struct uart_bridge_config {
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const struct device *peer_dev[2];
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};
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struct uart_bridge_peer_data {
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uint8_t buf[RING_BUF_SIZE];
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struct ring_buf rb;
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bool paused;
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};
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struct uart_bridge_data {
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struct uart_bridge_peer_data peer[2];
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};
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static const struct device *uart_bridge_get_peer(const struct device *dev,
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const struct device *bridge_dev)
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{
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const struct uart_bridge_config *cfg = bridge_dev->config;
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if (dev == cfg->peer_dev[0]) {
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return cfg->peer_dev[1];
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} else if (dev == cfg->peer_dev[1]) {
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return cfg->peer_dev[0];
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} else {
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return NULL;
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}
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}
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void uart_bridge_settings_update(const struct device *dev,
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const struct device *bridge_dev)
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{
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struct uart_config cfg;
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const struct device *peer_dev = uart_bridge_get_peer(dev, bridge_dev);
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int ret;
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if (peer_dev == NULL) {
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LOG_DBG("%s: not a bridge dev", dev->name);
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return;
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}
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LOG_DBG("update settings: dev=%s bridge=%s peer=%s", dev->name,
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bridge_dev->name, peer_dev->name);
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ret = uart_config_get(dev, &cfg);
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if (ret) {
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LOG_WRN("%s: failed to get the uart config: %d", dev->name,
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ret);
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return;
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}
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ret = uart_configure(peer_dev, &cfg);
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if (ret) {
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LOG_WRN("%s: failed to set the uart config: %d", peer_dev->name,
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ret);
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return;
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}
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LOG_INF("uart settings: baudrate=%d parity=%d", cfg.baudrate,
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cfg.parity);
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}
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static uint8_t uart_bridge_get_idx(const struct device *dev,
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const struct device *bridge_dev, bool own)
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{
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const struct uart_bridge_config *cfg = bridge_dev->config;
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if (dev == cfg->peer_dev[0]) {
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return own ? 0 : 1;
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} else {
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return own ? 1 : 0;
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}
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}
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static void uart_bridge_handle_rx(const struct device *dev,
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const struct device *bridge_dev)
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{
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const struct uart_bridge_config *cfg = bridge_dev->config;
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struct uart_bridge_data *data = bridge_dev->data;
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const struct device *peer_dev =
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cfg->peer_dev[uart_bridge_get_idx(dev, bridge_dev, false)];
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struct uart_bridge_peer_data *own_data =
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&data->peer[uart_bridge_get_idx(dev, bridge_dev, true)];
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uint8_t *recv_buf;
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int rb_len, recv_len;
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int ret;
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if (ring_buf_space_get(&own_data->rb) < RING_BUF_FULL_THRESHOLD) {
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LOG_DBG("%s: buffer full: pause", dev->name);
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uart_irq_rx_disable(dev);
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own_data->paused = true;
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return;
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}
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rb_len = ring_buf_put_claim(&own_data->rb, &recv_buf, RING_BUF_SIZE);
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if (rb_len == 0) {
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LOG_WRN("%s: ring_buf full", dev->name);
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return;
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}
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recv_len = uart_fifo_read(dev, recv_buf, rb_len);
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if (recv_len < 0) {
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ring_buf_put_finish(&own_data->rb, 0);
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LOG_ERR("%s: rx error: %d", dev->name, recv_len);
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return;
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}
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ret = ring_buf_put_finish(&own_data->rb, recv_len);
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if (ret < 0) {
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LOG_ERR("%s: ring_buf_put_finish error: %d", dev->name, rb_len);
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return;
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}
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uart_irq_tx_enable(peer_dev);
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}
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static void uart_bridge_handle_tx(const struct device *dev,
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const struct device *bridge_dev)
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{
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const struct uart_bridge_config *cfg = bridge_dev->config;
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struct uart_bridge_data *data = bridge_dev->data;
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const struct device *peer_dev =
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cfg->peer_dev[uart_bridge_get_idx(dev, bridge_dev, false)];
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struct uart_bridge_peer_data *peer_data =
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&data->peer[uart_bridge_get_idx(dev, bridge_dev, false)];
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uint8_t *send_buf;
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int rb_len, sent_len;
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int ret;
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rb_len = ring_buf_get_claim(&peer_data->rb, &send_buf, RING_BUF_SIZE);
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if (rb_len == 0) {
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LOG_DBG("%s: buffer empty, disable tx irq", dev->name);
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uart_irq_tx_disable(dev);
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return;
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}
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sent_len = uart_fifo_fill(dev, send_buf, rb_len);
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if (sent_len < 0) {
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ring_buf_get_finish(&peer_data->rb, 0);
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LOG_ERR("%s: tx error: %d", dev->name, sent_len);
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return;
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}
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ret = ring_buf_get_finish(&peer_data->rb, sent_len);
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if (ret < 0) {
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LOG_ERR("ring_buf_get_finish error: %d", ret);
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return;
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}
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if (peer_data->paused &&
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ring_buf_space_get(&peer_data->rb) > RING_BUF_FULL_THRESHOLD) {
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LOG_DBG("%s: buffer free: resume", dev->name);
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uart_irq_rx_enable(peer_dev);
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peer_data->paused = false;
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return;
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}
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}
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static void interrupt_handler(const struct device *dev, void *user_data)
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{
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const struct device *bridge_dev = user_data;
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while (uart_irq_update(dev) && uart_irq_is_pending(dev)) {
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if (uart_irq_rx_ready(dev)) {
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uart_bridge_handle_rx(dev, bridge_dev);
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}
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if (uart_irq_tx_ready(dev)) {
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uart_bridge_handle_tx(dev, bridge_dev);
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}
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}
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}
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static int uart_bridge_init(const struct device *dev)
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{
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const struct uart_bridge_config *cfg = dev->config;
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struct uart_bridge_data *data = dev->data;
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ring_buf_init(&data->peer[0].rb, RING_BUF_SIZE, data->peer[0].buf);
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ring_buf_init(&data->peer[1].rb, RING_BUF_SIZE, data->peer[1].buf);
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uart_irq_callback_user_data_set(cfg->peer_dev[0], interrupt_handler,
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(void *)dev);
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uart_irq_callback_user_data_set(cfg->peer_dev[1], interrupt_handler,
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(void *)dev);
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uart_irq_rx_enable(cfg->peer_dev[0]);
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uart_irq_rx_enable(cfg->peer_dev[1]);
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return 0;
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}
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#define UART_BRIDGE_INIT(n) \
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BUILD_ASSERT(DT_INST_PROP_LEN(n, peers) == 2, \
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"uart-bridge peers property must have exactly 2 members"); \
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\
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static const struct uart_bridge_config uart_bridge_cfg_##n = { \
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.peer_dev = {DT_INST_FOREACH_PROP_ELEM_SEP( \
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n, peers, DEVICE_DT_GET_BY_IDX, (,))}, \
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}; \
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\
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static struct uart_bridge_data uart_bridge_data_##n; \
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\
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DEVICE_DT_INST_DEFINE(n, uart_bridge_init, NULL(n), \
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&uart_bridge_data_##n, &uart_bridge_cfg_##n, \
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POST_KERNEL, CONFIG_SERIAL_INIT_PRIORITY, NULL);
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DT_INST_FOREACH_STATUS_OKAY(UART_BRIDGE_INIT)
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23
dts/bindings/serial/zephyr,uart-bridge.yaml
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23
dts/bindings/serial/zephyr,uart-bridge.yaml
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@ -0,0 +1,23 @@
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# Copyright 2025 Google LLC
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# SPDX-License-Identifier: Apache-2.0
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title: UART bridge
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description: |
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Bridges data between two serial devices, for example a USB CDC-ACM serial
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port and an hardware UART.
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The device node must specify exactly two peer phandles for the two serial
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devices to be bridged together. Example configuration:
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uart-bridge {
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compatible = "zephyr,uart-bridge";
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peers = <&cdc_acm_uart0 &uart1>;
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};
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compatible: "zephyr,uart-bridge"
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properties:
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peers:
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type: phandles
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description: Peer device nodes, must contain two phandles
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19
include/zephyr/drivers/uart/uart_bridge.h
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19
include/zephyr/drivers/uart/uart_bridge.h
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@ -0,0 +1,19 @@
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/*
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* Copyright 2025 Google LLC
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/device.h>
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/**
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* @brief Update the hardware port settings on a uart bridge
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*
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* If dev is part bridge_dev, then the dev uart configuration are applied to
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* the other device in the uart bridge. This allows propagating the settings
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* from a USB CDC-ACM port to a hardware UART.
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*
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* If dev is not part of bridge_dev then the function is a no-op.
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*/
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void uart_bridge_settings_update(const struct device *dev,
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const struct device *bridge_dev);
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