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Pieter ViljoenandClaude Opus 5.5
03f306b5b3
rtc_probe() decided from one read whether the device at a declared address was the RTC its descriptor expects: a valid BCD block including hours and year, or the power-loss flag set or unreadable. That skipped real RTCs whose year byte or hours another firmware left out of range (a year byte of A0 or more; 12-hour mode reads PM hours with bit 5 set), ruled nothing out by identity, and adopted an erased EEPROM through its 0xFF "status". - An optional zero-mask descriptor property holds the time-block bits a part's data sheet shows as 0. rtc-i2c.dtsi sets it for 0x68 (DS3231 19-5170 Rev 10 and DS3232 19-5337 Rev 5, Figure 1, p. 11; DS1307 Rev 3/15, Table 2, p. 8; 00h bit 7 left out, the DS1307's clock-halt bit), the RV3028 (App Manual Rev 1.4, 3.2, p. 12) and the RX8130CE (ETM50E-10, 13.2.1 Table 12, p. 22). The PCF8563 gets none: its data sheet (Rev 11.1, Table 4, p. 10) marks unused bits "not relevant". - One read rules a device out if a masked bit is set, or if seconds, minutes, date or month are out of range while the power-loss flag does not read as set. The year and hours are no longer identity checks. - A device is passed over only when two reads each rule it out. A failed first read means nothing is there; a failed second read does not count, and with no clean read the chip is adopted for write-back but gives no time. An all-0xFF second read rules the device out. - An all-0xFF first read is skipped, and the first save probes once more, since a real RTC can power up that way. - A time is restored only from a clean read whose fields, hours and year are all valid. The decision is one function, rtc_identify(). The same rules, with a few agreed differences, are in meshcore-dev/MeshCore#3544. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>