Question
Questions surrounding __HAL_LOCK
Posted on April 26, 2016 at 00:12
I’m an engineer at Fluke, and we’re using an STM32F4xx seriesmicrocontroller (together with its HAL drivers) as the basis for a newproduct. The HAL contains a “locking�? mechanism, where eachsubsystem—I²C, USB, UART, and so on—has a “locking object�?. My team hasbeen working on the assumption that this mechanism’s goal is to providesome mutual exclusion for memory-mapped hardware registers and relatedstate so that, for example, an interrupt doesn’t modify the same hardware state being manipulated in the main “thread�? of exectution.
What’s confused us, however, is how this is done. The driver code found in stm32f4xx_hal_def.h defines the locking mechanism as follows:[1]typedef
enum
{
HAL_UNLOCKED = 0x00U,
HAL_LOCKED = 0x01U
} HAL_LockTypeDef;
#if (USE_RTOS == 1)
/* Reserved for future use */
#error ''USE_RTOS should be 0 in the current HAL release''
#else
#define __HAL_LOCK(__HANDLE__) \
do
{ \
if
((__HANDLE__)->Lock == HAL_LOCKED) \
{ \
return
HAL_BUSY; \
} \
else
\
{ \
(__HANDLE__)->Lock = HAL_LOCKED; \
} \
}
while
(0)
#define __HAL_UNLOCK(__HANDLE__) \
do
{ \
(__HANDLE__)->Lock = HAL_UNLOCKED; \
}
while
(0)
#endif /* USE_RTOS */