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...
> > [ 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@xxxxxxxxx>
> > Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
> > Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
> > ---
> > 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
patches to linux-ide@ so issues can be spotted and discussed early...
Thanks,
Bart
--
To unsubscribe from this list: send the line "unsubscribe linux-ide" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
