mgmt: ec_host_cmd: add USB backend

Add a new ec_host_cmd backend based on USB. The backend uses the new USB
device stack.

The backend implements a vendor-specific (Google) USB interface. It uses
three endpoints:
- bulk OUT to transfer a host command request
- bulk IN to transfer a host command response
- interrupt IN to signal an event and readiness of the response

Signed-off-by: Dawid Niedzwiecki <[email protected]>

Author: niedzwiecki-dawid

include/zephyr/mgmt/ec_host_cmd/backend.h

@@ -162,6 +162,14 @@ struct ec_host_cmd_backend *ec_host_cmd_backend_get_uart(const struct device *de
  */
 struct ec_host_cmd_backend *ec_host_cmd_backend_get_spi(struct gpio_dt_spec *cs);
 
+/**
+ * @brief Signal event over USB
+ *
+ * Signal event using USB interrupt endpoint. It informs host that there is a pending event that has
+ * to be handled. The function performs remote wake-up if needed.
+ */
+void ec_host_cmd_backend_usb_trigger_event(void);
+
 /**
  * @}
  */

subsys/mgmt/ec_host_cmd/Kconfig

@@ -49,6 +49,7 @@ config EC_HOST_CMD_HANDLER_RX_BUFFER_SIZE
 
 config EC_HOST_CMD_HANDLER_BUFFER_ALIGN
 	int "Memory alignment for the tx/rx buffers"
+	default DCACHE_LINE_SIZE if (DCACHE_LINE_SIZE > 0) && EC_HOST_CMD_BACKEND_USB
 	default 4
 	help
 	  Some interfaces need a special memory alignment to work properly. Use that config

subsys/mgmt/ec_host_cmd/backends/CMakeLists.txt

@@ -25,3 +25,7 @@ zephyr_library_sources_ifdef(
 zephyr_library_sources_ifdef(
 	CONFIG_EC_HOST_CMD_BACKEND_SPI_STM32
 	ec_host_cmd_backend_spi_stm32.c)
+
+zephyr_library_sources_ifdef(
+	CONFIG_EC_HOST_CMD_BACKEND_USB
+	ec_host_cmd_backend_usb.c)

subsys/mgmt/ec_host_cmd/backends/Kconfig

@@ -132,3 +132,10 @@ config EC_HOST_CMD_BACKEND_UART_TIMEOUT
 	  chunk.
 
 endif # EC_HOST_CMD_BACKEND_UART
+
+config EC_HOST_CMD_BACKEND_USB
+	bool "Host commands support using USB"
+	default y
+	depends on USB_DEVICE_STACK_NEXT
+	help
+	  Enable support for Embedded Controller host commands using the USB.