Messages in this thread | | | Date | Tue, 28 Oct 2008 00:28:00 -0400 | From | Jeff Garzik <> | Subject | Re: [PATCH] ata: ata_id_is_ssd() bugfix |
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Jens Axboe wrote: > On Sun, Oct 19 2008, Bartlomiej Zolnierkiewicz wrote: >> On Sunday 19 October 2008, Jens Axboe wrote: >>> On Sat, Oct 18 2008, Bartlomiej Zolnierkiewicz wrote: >>>> We need to explicitly check for major and minor version >>>> of supported ATA spec as earlier revisions used word 217 >>>> for different purposes. >>> What did they use to put in that word? Just curious if it does any harm, >>> >>> because as it stands, this patch will prevent ANY ssd from being >>> correctly flagged as such. So I'm inclined to file this as too much spec >>> fiddling, it'll do more harm than good. >> IIRC it was marked as Reserved for < ATA8 (however I didn't go through >> all previous specs) and some ATA8 minor versions (i.e. 3f) put "NV Cache >> Read Transfer Speed in MB/s" there. >> >> Well, we may also drop minor versions checking assuming that no NV Cache >> actually will have 1MB/s speed and major version checking assuming that >> no vendor put anything special there but this would need an ACK from Alan >> and maybe a comment on why we do it... > > OK, so it's just NV cache. I'd consider that a non-issue. > >>>> [ The issue was originally spotted by Alan Cox. ] >>>> >>>> This patch fixes regression introduced by: >>>> commit 8bff7c6b0f63c7ee9c5e3a076338d74125b8debb >>>> ("libata: set queue SSD flag for SSD devices"). >>>> >>>> Cc: Jeff Garzik <jgarzik@pobox.com> >>>> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> >>>> Cc: Jens Axboe <jens.axboe@oracle.com> >>>> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> >>>> --- >>>> somebody owe me one for going through all these spec drafts... ;) >>>> >>>> include/linux/ata.h | 8 +++++++- >>>> 1 file changed, 7 insertions(+), 1 deletion(-) >>>> >>>> Index: b/include/linux/ata.h >>>> =================================================================== >>>> --- a/include/linux/ata.h >>>> +++ b/include/linux/ata.h >>>> @@ -75,6 +75,7 @@ enum { >>>> ATA_ID_EIDE_PIO_IORDY = 68, >>>> ATA_ID_QUEUE_DEPTH = 75, >>>> ATA_ID_MAJOR_VER = 80, >>>> + ATA_ID_MINOR_VER = 81, >>>> ATA_ID_COMMAND_SET_1 = 82, >>>> ATA_ID_COMMAND_SET_2 = 83, >>>> ATA_ID_CFSSE = 84, >>>> @@ -743,7 +744,12 @@ static inline int ata_id_is_cfa(const u1 >>>> >>>> static inline int ata_id_is_ssd(const u16 *id) >>>> { >>>> - return id[ATA_ID_ROT_SPEED] == 0x01; >>>> + /* ATA8-ACS version 4c or higher (=> 4c or 6 at the moment) */ >>>> + if (ata_id_major_version(id) >= 8 && >>>> + (id[ATA_ID_MINOR_VER] == 0x39 || id[ATA_ID_MINOR_VER] == 0x28) && >>>> + id[ATA_ID_ROT_SPEED] == 0x01) >>>> + return 1; >>>> + return 0; >>> Is the check even correct? It'll match version 8 AND the currently >>> listed minor version, not newer. >> Checking minor versions is a non-trivial bussiness and improvements >> are welcomed (though ATA8-ACS version 6 is the newest revision ATM). >> >> It could also be that the we should be checking something else than >> the ATA_ID_ROT_SPEED to detect SSDs reliably but I don't know and don't >> have time currently to look into it. In the future please post ATA > > Rotation speed == 1 is THE way to check for an SSD. The problem is just > that lots of drives are out there and don't claim ATA8 compliance, since > it was finalized until last month. Most of them SHOULD use word 217 > though, the ones I looked at sure do.
It seems highly unlikely that any drive that claims ATA8 would repurpose word 217, therefore upstream logic IMO should look like
if (id[ATA_ID_ROT_SPEED] == 0x01 && ((ata_id_major_version(id) >= 8) || (a list of ATA6/7 exceptions that Jens wishes to supply)))
Regards,
Jeff
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