UNDEF_REG          40 drivers/irqchip/irq-stm32-exti.c #define UNDEF_REG ~0
UNDEF_REG          90 drivers/rtc/rtc-stm32.c #define UNDEF_REG			0xFFFF
UNDEF_REG          38 drivers/tty/serial/stm32-usart.h #define UNDEF_REG 0xff