harden USB telemetry transport

main/trikke_usb_transport.c

@@ -0,0 +1,92 @@
+#include "trikke_usb_transport.h"
+
+#include "driver/usb_serial_jtag.h"
+#include "driver/usb_serial_jtag_vfs.h"
+#include "freertos/FreeRTOS.h"
+
+#define TRIKKE_USB_TX_BUFFER_SIZE 512
+#define TRIKKE_USB_RX_BUFFER_SIZE 128
+#define TRIKKE_USB_OPERATION_TIMEOUT_MS 50
+
+static trikke_transport_status_t usb_begin_packet(
+    void *context,
+    const uint8_t *packet,
+    size_t packet_size)
+{
+    const trikke_usb_transport_t *usb = context;
+    if (usb == NULL || !usb->initialized || packet == NULL || packet_size == 0 ||
+        packet_size > TRIKKE_USB_TX_BUFFER_SIZE) {
+        return TRIKKE_TRANSPORT_FATAL;
+    }
+
+    const int written = usb_serial_jtag_write_bytes(
+        packet, packet_size,
+        pdMS_TO_TICKS(TRIKKE_USB_OPERATION_TIMEOUT_MS));
+    if (written == (int)packet_size) {
+        return TRIKKE_TRANSPORT_PENDING;
+    }
+    if (written == 0) {
+        return TRIKKE_TRANSPORT_RETRY;
+    }
+    return TRIKKE_TRANSPORT_FATAL;
+}
+
+static trikke_transport_status_t usb_poll_packet(void *context)
+{
+    const trikke_usb_transport_t *usb = context;
+    if (usb == NULL || !usb->initialized) {
+        return TRIKKE_TRANSPORT_FATAL;
+    }
+
+    const esp_err_t err = usb_serial_jtag_wait_tx_done(
+        pdMS_TO_TICKS(TRIKKE_USB_OPERATION_TIMEOUT_MS));
+    if (err == ESP_OK) {
+        return TRIKKE_TRANSPORT_COMPLETE;
+    }
+    if (err == ESP_ERR_TIMEOUT) {
+        return TRIKKE_TRANSPORT_PENDING;
+    }
+    return TRIKKE_TRANSPORT_FATAL;
+}
+
+esp_err_t trikke_usb_transport_init(
+    trikke_usb_transport_t *usb,
+    trikke_transport_t *transport)
+{
+    if (usb == NULL || transport == NULL) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    if (usb->initialized) {
+        return ESP_ERR_INVALID_STATE;
+    }
+
+    usb_serial_jtag_driver_config_t config = {
+        .tx_buffer_size = TRIKKE_USB_TX_BUFFER_SIZE,
+        .rx_buffer_size = TRIKKE_USB_RX_BUFFER_SIZE,
+    };
+    const esp_err_t err = usb_serial_jtag_driver_install(&config);
+    if (err != ESP_OK) {
+        return err;
+    }
+
+    usb->initialized = true;
+    transport->context = usb;
+    transport->begin = usb_begin_packet;
+    transport->poll = usb_poll_packet;
+
+    // Route any unexpected VFS output through the installed driver as well, so
+    // it cannot race the driver's ISR by touching the hardware FIFO directly.
+    usb_serial_jtag_vfs_use_driver();
+    return ESP_OK;
+}
+
+void trikke_usb_transport_deinit(trikke_usb_transport_t *usb)
+{
+    if (usb == NULL || !usb->initialized) {
+        return;
+    }
+
+    usb_serial_jtag_vfs_use_nonblocking();
+    usb_serial_jtag_driver_uninstall();
+    usb->initialized = false;
+}