From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from omr1.cc.ipv6.vt.edu ([2607:b400:92:8300:0:c6:2117:b0e] helo=omr1.cc.vt.edu) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1b7UG6-0001hF-FC for linux-mtd@lists.infradead.org; Mon, 30 May 2016 20:57:59 +0000 To: Boris Brezillon Cc: Richard Weinberger , linux-mtd@lists.infradead.org, David Woodhouse , Brian Norris , Hans de Goede , linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/15] mtd: nand: samsung: retrieve ECC requirements from extended ID From: Valdis.Kletnieks@vt.edu In-Reply-To: <20160530094446.5edec3ac@bbrezillon> References: <1464353701-23233-1-git-send-email-boris.brezillon@free-electrons.com> <1464353701-23233-14-git-send-email-boris.brezillon@free-electrons.com> <198040.1464567635@turing-police.cc.vt.edu> <20160530094446.5edec3ac@bbrezillon> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1464641769_2071P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Mon, 30 May 2016 16:56:09 -0400 Message-ID: <137285.1464641769@turing-police.cc.vt.edu> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --==_Exmh_1464641769_2071P Content-Type: text/plain; charset=us-ascii On Mon, 30 May 2016 09:44:46 +0200, Boris Brezillon said: > Hi Valdis, > Actually, that was my first reaction [1], but the more I think about it > the more I realize it's a non-issue. > AFAICT, there's no full-id entries for Samsung NANDs in the nand_ids > table, so this either means there's no real users of Samsung MLCs or > NAND controller drivers connecting to those chips don't care about the > ->ecc_{step_ds,strength_ds} fields. I'm mostly, though not totally convinced (not having looked closely at the existing code). There's still a possible issue with the distinction between: A) "driver never references the variable" and B) driver check if it's zero, and acts like it doesn't care if it is, but if it's non-zero, it goes ahead and uses it, with possible hilarity ensuing if the value is wrong. Should be pretty easy for somebody who knows the code better than I to rule out case B fairly quickly... > I agree that the solution is not perfect, but I'd prefer seeing the > NAND detection code iteratively improved than rejecting everything > until we're 100% sure that all cases are correctly handled (which might > never happen since NAND vendors introduce new NAND ID scheme if they > need to). > > BTW, do you have Samsung datasheets describing a different NAND ID > format, or is it purely hypothetical? Mostly hypothetical. I've just seen too many patches that assume "all chips from vendor XYZ do *this*" that were not at all corrrect. --==_Exmh_1464641769_2071P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Exmh version 2.5 07/13/2001 iQIVAwUBV0yo6QdmEQWDXROgAQIX5BAAoQW268qTXx0WZt/1U7B/AHt6kdCKAu+6 eGVaNN3HUTt+TwqSonHxfhapwNjMAKAI79lGpxJMaDbf+eBtg0zmIpjr+vaCmPfG ag8eVMIXA7pmlVOF989ckwDVQxz0wl0y+6UoGH99B2+NRCF7k16cRmLHHP4WkXOJ 5TtCZm8O867L3CJ44b+isu1kq6iKBgSMtExEJs2bpbjxXDGEyVBQ/1Al+7sQXed6 UpptQCzLVAiqrbH6aNp0PA5iq5n2w1J/O1OolHOCqDYuHKOVzOIYPb/sYXzeYy0u saRm/5ZZEuQcB0S2msmDpSn94JZmc4VUkuX9YymoDfO5eilDlK7p1jpCDxiK984D TUWBs63Aps4yMp9+pkUepgCkP7Y30ZbwiK7ONFjbgUW5yvE8IZYkz8uE0XCKGROY Zwv2KUCfXQR76Vuy9PSqYlHo5VVGg92Rvj19OaINkPCspS9Vze9KoFc5RCEU96l1 2RU2a+svJXNrB8qaD5YpaEysmUp4VnXWzOiXyd/98PigS5CCsSEpaekzWWddmrmG uMph4wRyUCGVDMxAukhev7mlt60Wr0NY5kO4qmyOa8CfsUoA2zxePSRqgYIr2U9j Nt/6z8VctDGf0pPyTojlQlffpt+QU9Ebz5nOIGExM3JtbOQQtGc4scv8dfYN424B S45cfP6Byys= =L//p -----END PGP SIGNATURE----- --==_Exmh_1464641769_2071P--