sync.c

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#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/*----- Header-Files -------------------------------------------------------*/
#include <_ansi.h>                  /* support for ANSI environments        */
#include <stm32f4xx.h>              /* Processor STM32F407IG                */
#include <stddef.h>                 /* Standard defines                     */
#include <ff.h>                     /* Fat file system                      */

#if _FS_REENTRANT

/*----- Macros -------------------------------------------------------------*/

/*----- Data types ---------------------------------------------------------*/

/*----- Function prototypes ------------------------------------------------*/

/*----- Data ---------------------------------------------------------------*/
_VOLATILE static uint8_t sync[_VOLUMES];

/*----- Implementation -----------------------------------------------------*/
__attribute__((naked)) static uint32_t DisableGlobalInterrupt(void) {
    __asm volatile
    (
            "   mrs r0, basepri                                         \n"
            "   mov r1, %0                                              \n"
            "   msr basepri, r1                                         \n"
            "   bx lr                                                   \n"
            :: "i" (255) : "r0", "r1"
    );

    /* This return will not be reached but is necessary to prevent compiler
     * warnings.                                                            */
    return 0;
}

__attribute__((naked)) static void EnableGlobalInterrupt(
        uint32_t ulNewMaskValue) {
    __asm volatile
    (
            "   msr basepri, r0                                     \n"
            "   bx lr                                               \n"
            :::"r0"
    );

    /* Just to avoid compiler warnings. */
    (void) ulNewMaskValue;
}

__attribute__((weak)) int ff_cre_syncobj(BYTE vol, _SYNC_t *mutex) {

    _VOLATILE uint8_t **value = (_VOLATILE uint8_t **)mutex;

    /* Check if the drive number is valid */
    if (vol >= _VOLUMES) {
        return FR_INVALID_DRIVE;
    }

    /* Get current fs object */
    *value = &sync[vol];

    return (*mutex != NULL);
}

__attribute__((weak)) int ff_del_syncobj(_SYNC_t mutex) {

    uint8_t *value = (uint8_t *)mutex;
    uint32_t interrupts;

    interrupts = DisableGlobalInterrupt();
    *value = 0;
    EnableGlobalInterrupt(interrupts);

    return !0;
}

__attribute__((weak)) int ff_req_grant(_SYNC_t mutex) {

    uint8_t *value = (uint8_t *)mutex;
    uint32_t interrupts;
    uint8_t granted = 0;

    interrupts = DisableGlobalInterrupt();
    if (!(*value)) {
        *value = 1;
        granted = 1;
    }
    EnableGlobalInterrupt(interrupts);

    return granted;
}

__attribute__((weak)) void ff_rel_grant(_SYNC_t mutex) {

    uint8_t *value = (uint8_t *)mutex;
    uint32_t interrupts;

    interrupts = DisableGlobalInterrupt();
    *value = 0;
    EnableGlobalInterrupt(interrupts);
}

#endif /* _FS_REENTRANT */

#ifdef __cplusplus
}
#endif /* __cplusplus */