Validate Configuration Register Layout

Code

#include <stdio.h>

typedef struct {
    union {
    unsigned short reg;
    struct {
        unsigned enable   : 1;
        unsigned mode     : 1;
        unsigned priority : 2;
        unsigned reserved : 12;
        } bits;
    };
} ConfigRegister;

int validate_config(ConfigRegister *cfg) {
    // Write logic using pointer access
    //printf("%d %d %d\n", cfg->bits.enable, cfg->bits.priority, cfg->bits.reserved);
    if (cfg->bits.enable != 1)
        return 0;
    if (cfg->bits.priority == 3)
        return 0;
    if (cfg->bits.reserved != 0)
        return 0;
    return 1;
}

int main() 
{
    ConfigRegister cfg;
    scanf("%hx", &cfg.reg);

    /*
    printf("\ncfg.reg%hX: ", cfg.reg);
    printf("enable:%hX ", cfg.bits.enable);
    printf("mode:%hX ", cfg.bits.mode);
    printf("priority: %hX: ", cfg.bits.priority);
    printf("reserved: %hX\n", cfg.bits.reserved);
    */
    
    int result = validate_config(&cfg);
    printf("%d", result);

    return 0;
}

Solving Approach

create a type struct to define the bit fields.

modify configuration register to be a union of the unsigned short and the bit fields for easy identification.