Re: Changes to ide-probe.c in 2.6.9-rc2 causing improper detection

[Jeff Garzik]

Alan Cox wrote:
> On Maw, 2004-09-14 at 07:06, Jens Axboe wrote:
>
> > Alan, I bet there are a lot of these. Maybe we should consider letting
> > the user manually flag support for FLUSH_CACHE, at least it is in their
> > hands then.
>
>
> You are assuming the drive supports "FLUSH_CACHE" just because it
> doesn't error it. Thats a good way to have accidents. 
>
> The patch I posted originally did turn wcache off for barrier if no
> flush cache support was present but had a small bug so that bit got
> dropped.


FWIW the libata test for checking whether it is OK to issue a flush is

        return ata_id_wcache_enabled(dev) ||
               ata_id_has_flush(dev) ||
               ata_id_has_flush_ext(dev);

and if it passes that test,

        if ((tf->flags & ATA_TFLAG_LBA48) &&
            (ata_id_has_flush_ext(qc->dev)))
                tf->command = ATA_CMD_FLUSH_EXT;
        else
                tf->command = ATA_CMD_FLUSH;

I wouldn't object to removing the "ata_id_wcache_enabled" test if people 
feel that it is unsafe.

	Jeff


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