[BUG] ata: disk_ata_drive: SSD drive doesn't pass check for ata id validity

[Juergen Borleis]

On Friday 30 October 2015 08:31:04 Sascha Hauer wrote:
> On Thu, Oct 29, 2015 at 04:04:09PM +0300, Peter Mamonov wrote:
> > Hi!
> >
> > Barebox refuses to deal with OCZ-VERTEX4 ssd sata drive, because:
> > 	ata1: ata id invalid
> >
> > This error is triggered by the following piece of code :
> >
> > static int ata_id_is_valid(const uint16_t *id)
> > {
> > 	if ((id[ATA_ID_FIELD_VALID] & 1) == 0) {
> > 		pr_debug("Drive's ID seems invalid\n");
> > 		return -EINVAL;
> > 	}
> >
> > 	return 0;
> > }
> >
> > The "id" is a sector-sized block of bytes, received after
> > issuing ATA_CMD_ID_ATA command.
> >
> > If I remove this check, the drive works fine.
> >
> > Can someone with better knowledge of ATA standard comment on this
> > issue?
>
> Juergen, do you have an idea what this check is for? Neither U-Boot nor
> the Kernel seem to ever check for bit 0 in this field.

Seems this bit was meaningful in earlier days: it marked the ID member in the 
structure returned by the disk as valid (=1) or invalid (=0). In the meantime 
it seems obsolete. The last occurrence I found is in the Linux kernel in 
file "drivers/block/mg_disk.c". All other code which checks this register 
content just check bits 1 and 2. I vote for removing this piece of code.

jbe

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Pengutronix e.K.                              | Juergen Borleis             |
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