RTC_BYTES
#define RTC_BITS (8 * RTC_BYTES)
ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
if (ret != RTC_BYTES)
if (len < RTC_BYTES) {
memcpy(&off, p_off, RTC_BYTES);
ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
if (ret != RTC_BYTES)
return nvmem_cell_write(rtc->rtc_offset, &off, RTC_BYTES);