From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752611Ab1KMNDZ (ORCPT ); Sun, 13 Nov 2011 08:03:25 -0500 Received: from casper.infradead.org ([85.118.1.10]:53232 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751437Ab1KMNDY (ORCPT ); Sun, 13 Nov 2011 08:03:24 -0500 Message-ID: <1321189398.2021.5.camel@shinybook.infradead.org> Subject: Re: [PATCH v2 07/16] mtd/docg3: add OOB layout to mtdinfo From: David Woodhouse To: dedekind1@gmail.com Cc: Robert Jarzmik , Mike Dunn , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org Date: Sun, 13 Nov 2011 13:03:18 +0000 In-Reply-To: <1321188825.2273.4.camel@koala> References: <1320912342-30147-1-git-send-email-robert.jarzmik@free.fr> <1320912342-30147-8-git-send-email-robert.jarzmik@free.fr> <4EBECB89.2020102@newsguy.com> <87vcqoiavr.fsf@free.fr> <1321188825.2273.4.camel@koala> Content-Type: multipart/signed; micalg="sha1"; protocol="application/x-pkcs7-signature"; boundary="=-FcpChSA1wNBKqITB5xIE" X-Mailer: Evolution 3.2.1 (3.2.1-2.fc16) Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-FcpChSA1wNBKqITB5xIE Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2011-11-13 at 14:53 +0200, Artem Bityutskiy wrote: > On Sun, 2011-11-13 at 11:18 +0100, Robert Jarzmik wrote: > > I personally think this should be provided by the MTD API. A function > > is_page_blank(ofs) could tell if the page was written or not. Now if th= e > > function is NULL, the upper layer (UBIFS, ...) could decide _by itself_= to > > assign a free OOB byte to that meaning. But IMHO it's not the drivers d= uty to > > take these decisions to restrict the OOB, let it be done at an upper le= vel. >=20 > Probably it is a good idea to introduce an mtd_is_page_blank. But it > should either work for all flashes or not introduced at all. I do not > think upper layers should use OOB at all. And this interface should also > work for NOR flash. Probably it should just fall-back to comparing the > data with 0xFF if the driver cannot offer anything special.=20 We *tried* comparing with 0xFF in JFFS2 and found that it wasn't good enough (it could be *mostly* erased before a powerfail but not completely, so as soon as you start to program it you get a lot of bitflips). Hence the cleanmarkers. The only way you can treat a page as erased is if you *know* it was successfully erased. So I'd be reluctant to introduce a function that encourages people to draw inferences they shouldn't. --=20 dwmw2 --=-FcpChSA1wNBKqITB5xIE Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIITvzCCBi0w ggQVoAMCAQICAwCtOTANBgkqhkiG9w0BAQUFADBUMRQwEgYDVQQKEwtDQWNlcnQgSW5jLjEeMBwG A1UECxMVaHR0cDovL3d3dy5DQWNlcnQub3JnMRwwGgYDVQQDExNDQWNlcnQgQ2xhc3MgMyBSb290 MB4XDTEwMDYxMjEwMDMwMFoXDTEyMDYxMTEwMDMwMFowgegxGDAWBgNVBAMTD0RhdmlkIFdvb2Ro b3VzZTEiMCAGCSqGSIb3DQEJARYTZHdtdzJAaW5mcmFkZWFkLm9yZzEfMB0GCSqGSIb3DQEJARYQ ZGF2aWRAd29vZGhvdS5zZTEoMCYGCSqGSIb3DQEJARYZZGF2aWQud29vZGhvdXNlQGludGVsLmNv bTEkMCIGCSqGSIb3DQEJARYVZHdtdzJAbGludXguaW50ZWwuY29tMTcwNQYJKoZIhvcNAQkBFigx MDg3MmEwN2Y2ZDdlMWUwN2Y1NWZmMTcyYTAzYjMwMGVlYWFkMjAzMIIBIjANBgkqhkiG9w0BAQEF AAOCAQ8AMIIBCgKCAQEA29OPhNvMxBMW83psWdVhZDtmJvgN+tBEp1r6MZamONsR0k81a6fDFwJz 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