serial_irq: Support side channel for entering bootloader

Add a mechanism to request the bootloader when using serial input.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/Kconfig

@@ -44,6 +44,8 @@ source "src/simulator/Kconfig"
 # Generic configuration options for serial ports
 config SERIAL
     bool
+config SERIAL_BOOTLOADER_SIDECHANNEL
+    bool
 config SERIAL_BAUD
     depends on SERIAL
     int "Baud rate for serial port" if LOW_LEVEL_OPTIONS

src/generic/serial_irq.c

@@ -79,6 +79,9 @@ console_task(void)
     if (ret > 0)
         command_dispatch(receive_buf, pop_count);
     if (ret) {
+        if (CONFIG_SERIAL_BOOTLOADER_SIDECHANNEL && ret < 0 && pop_count == 32
+            && !memcmp(receive_buf, " \x1c Request Serial Bootloader!! ~", 32))
+            bootloader_request();
         console_pop_input(pop_count);
         if (ret > 0)
             command_send_ack();

src/lpc176x/Kconfig

@@ -14,6 +14,7 @@ config LPC_SELECT
     select HAVE_CHIPID
     select HAVE_GPIO_HARD_PWM
     select HAVE_STEPPER_BOTH_EDGE
+    select SERIAL_BOOTLOADER_SIDECHANNEL
 
 config BOARD_DIRECTORY
     string

src/stm32/Kconfig

@@ -14,6 +14,7 @@ config STM32_SELECT
     select HAVE_STRICT_TIMING
     select HAVE_CHIPID
     select HAVE_STEPPER_BOTH_EDGE
+    select SERIAL_BOOTLOADER_SIDECHANNEL
 
 config BOARD_DIRECTORY
     string