test.c

#include <stdio.h>

typedef unsigned long uint64;

#define BIT(x) (1ULL << (uint64)(x))
#define GENMASK(msb, lsb) ((BIT(((uint64)(msb) + 1ULL) - (uint64)(lsb)) - 1ULL) << (uint64)(lsb))
#define _FIELD_LSB(field) ((uint64)(field) & ~((uint64)(field) - 1ULL))
#define FIELD_PREP(field, val) ((uint64)(val) * (_FIELD_LSB((uint64)field)))
#define FIELD_GET(field, val) (((uint64)(val) & (uint64)(field)) / _FIELD_LSB((uint64)(field)))

/* XYZOFFSET Fields */
#define GS_XYOFFSET_OFY GENMASK(47, 32)
#define GS_XYOFFSET_OFX GENMASK(15, 0)

void test(int height) {
	printf("height %d\n", height);
	printf("working %llx\n", FIELD_PREP(GS_XYOFFSET_OFY, (2048 - 448    / 2) << 4));
	printf("broken %llx\n",  FIELD_PREP(GS_XYOFFSET_OFY, (2048 - height / 2) << 4));
}

int main() {
    test(448);

    while (1)
	;


    return 0;
}