Am 08.12.2017 um 21:09 schrieb Sven Van Asbroeck: > On Fri, Dec 8, 2017 at 2:33 PM, Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote: >> In at24_adjust_read_count() there is the line >> remainder = BIT(bits) - offset; >> >> AFAICS we can have the case offset > BIT(bits). Imagine a 8 bit chip >> with size 512 (2 addresses) and we try to read a few bytes from >> offset 300. Then the line in question doesn't do what it's supposed >> to do. > > I don't think offset can be > BIT(bits). In at24_regmap_read(), we have: > > at24_client = at24_translate_offset(at24, &offset); > regmap = at24_client->regmap; > client = at24_client->client; > count = at24_adjust_read_count(at24, offset, count); > > at24_translate_offset() will translate the general offset to an offset > within a subchip. E.g. offset 300 will be translated to offset 44 > into the second subchip. > Ahh, I see that I misunderstood the issue being addressed by this change. Forget about my comments and sorry for the noise. >> And a more general aspect: If the size is 512 but only 256 byte are >> accessible then I doubt it's nice to create a nvmem provider with >> size 512. Wouldn't it be better to adjust byte_len to reflect the >> accessible size? Then we also wouldn't need the check in >> at24_adjust_read_count. > > I'm not sure if I understand. Could you clarify a bit Heiner? > If the size is 512 and it's a multi-address chip with 8-bit > addresses, we simply have two 256-byte subchips. > The size is 512. All 512 bytes are accessible. >
