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) {
    // len bits: ((0x1 << len) - 0x1)
    // mask: (lenbits << pos)
    // apply mask: reg | mask
    return reg | (((0x1 << len) - 0x1) << pos);
}

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;
}