Charles/Christian One problem with Christian's proposal is that it fails to distinguish between a totally failed read and an error corrected read. If the return values from readChunkFromNAND can differentiate the two states that may be helpful in the future. Nick Bane ----- Original Message ----- From: "Charles Manning" To: "Christian Gan" ; "Nick Bane" ; "yaffs list" Sent: Thursday, February 27, 2003 9:01 PM Subject: Re: yaffs: serious error in yaffs guts > Hi Christian > > It is easiest for me if someone using the Linux MTD with NANDECC can test > this. Otherewise I will have to write a software emulator. > > Could you roll this together with Thomas' recent patchs for NANDECC, with > your proposed ammendments, and I can apply them as a consistent patch set. > > Thanx > > -- Charles > > > On Fri, 28 Feb 2003 06:27, Christian Gan wrote: > > Also, > > > > In yaffs_guts there is no real need to check eccres1 and eccres2 you should > > only need to check the return value of nandmtd_ReadChunkFromNand. The two > > extra ints from the NAND MTD are only useful when you are performing > > multiple page reads when calling nand_read_ecc, since they will tell you > > which of the pages you requested has failed. But YAFFs only a reads single > > page at a time, looking at the return value of nand_read_ecc is enough to > > know if the write was successful or if an ecc error has occurred for that > > page. This value is checked in nandmtd_ReadChunkFromNand and it passes on > > a YAFFS_OK or YAFFS_FAIL (for any ecc errors) appropriately. > > > > Christian > > > > > -----Original Message----- > > > From: Nick Bane [mailto:nick@cecomputing.co.uk] > > > Sent: Thursday, February 27, 2003 10:31 AM > > > To: yaffs list > > > Subject: yaffs: serious error in yaffs guts > > > > > > > > > Charles > > > > > > A couple of bugs. One serious, one minor. > > > > > > in yaffs_ReadChunkFromNAND when dev->useNANDECC is true, it is > > > assumed that > > > readChunkFromNAND fills in the two ecc result integers on the end > > > of the oob > > > data. > > > These are then tested to see if there has been and ecc read > > > fail/correction > > > by the mtd layer. > > > > > > The problem with this is that readChunkFromNAND never actually passes the > > > ecc correction data back but leaves it in a local variable > > > tmpSpare and only > > > copies YAFFS_BYTES_PER_SPARE from it. > > > > > > The serious consequence of this is that all chunk reads are then > > > flagged as > > > failures and their blocks are marked as needing retiring once the data is > > > erased so yaffs nand becomes effectively write-once. The really serious > > > consequence of this is that one cannot now distinguish between > > > yaffs_retired_blocks and nand_factory_bad_blocks so one has to > > > speculatively > > > erase the entire device losing the factory erase data (which seems to be > > > zero on devices I have seen). Shouldn't we use a value other than 0 for > > > yaffs to mark the block as bad (with more than two zero bits) so > > > they can be > > > distinguished? > > > > > > The other bug is in testing the ecc correction results in > > > yaffs_ReadChunkFromNAND. > > > if(nspare.eccres2 || nspare.eccres2) > > > Clearly one of them should be eccres1 > > > > > > Nick > > > > > > ------------------------------------------- > > > Nick Bane > > > Cambridge, UK. > > > +44(0)1954 719270 > > > > > > > > > > > > > > > ------------------------------------------------------------------ > > > --------------------- > > > This mailing list is hosted by Toby Churchill open software > > > > (www.toby-churchill.org). > > If mailing list membership is no longer wanted you can remove yourself from > > the list by > > sending an email to yaffs-request@toby-churchill.org with the text > > "unsubscribe" > > (without the quotes) as the subject. > > > > > > -------------------------------------------------------------------------- - > >------------ This mailing list is hosted by Toby Churchill open software > > (www.toby-churchill.org). If mailing list membership is no longer wanted > > you can remove yourself from the list by sending an email to > > yaffs-request@toby-churchill.org with the text "unsubscribe" (without the > > quotes) as the subject. > > --------------------------------------------------------------------------------------- This mailing list is hosted by Toby Churchill open software (www.toby-churchill.org). If mailing list membership is no longer wanted you can remove yourself from the list by sending an email to yaffs-request@toby-churchill.org with the text "unsubscribe" (without the quotes) as the subject.