MEMCPY_BOUNCE_SIZE
char bounce[MEMCPY_BOUNCE_SIZE];
while (len >= MEMCPY_BOUNCE_SIZE) {
memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE);
memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE);
_src += MEMCPY_BOUNCE_SIZE;
_dst += MEMCPY_BOUNCE_SIZE;
len -= MEMCPY_BOUNCE_SIZE;
memcpy_fromio(bounce, _src, MEMCPY_BOUNCE_SIZE);
memcpy_toio(_dst, bounce, MEMCPY_BOUNCE_SIZE);