Set Specific Bits in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t set_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    uint32_t mask = 1;
    uint32_t data = reg;
    mask =  mask << pos;
    for (int i=0;i< len-1; i++){
        mask = mask | (mask<<1);
    }
    data = data | mask;

    return data;
}

int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%u", set_bits(reg, pos, len));
    return 0;
}