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SubjectRe: [PATCH] libata ATA vs SATA detection and workaround.
Brad Campbell wrote:
> + /* limit bridge transfers to udma5, 200 sectors */
> + if ((ap->cbl == ATA_CBL_SATA) && (!ata_id_is_sata(ap->device))) {
> + printk(KERN_INFO "ata%u(%u): applying bridge limits\n",
> + ap->id, ap->device->devno);
> + ap->udma_mask &= ATA_UDMA5;
> + ap->host->max_sectors = ATA_MAX_SECTORS;
> + ap->host->hostt->max_sectors = ATA_MAX_SECTORS;
> + ap->device->flags |= ATA_DFLAG_LOCK_SECTORS;
> + }
> if (ap->ops->dev_config)
> ap->ops->dev_config(ap, &ap->device[i]);


Close! Please move the entire quoted section, including the two lines
of code calling ->dev_config(), into a new function 'ata_dev_config'.
Export it (bottom of libata-core.c) and prototype it (libata.h) as well.

I'm still pondering what Alan was hinting at, a bit. You (Brad) are
correct in pointing out that this code should only trigger for the
correct situations (lba48, etc.) which are only present on modern
drives, but... there is still a chance that word 93 will be zero on
some weird (probably non-compliant) device.

However, Alan's comment is actually more relevant for unrelated sections
of libata. Whenever we test a feature bit in words 82-87, we should
check for "word != 0 && word != 0xffff" which is how one knows the word
is implemented. There are no feature bits indicating that feature bits
exist :)

Jeff


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