Re: [PATCH v1 4/4] ata: libata-scsi: Fix offsets for the fixed format sense data

[Igor Pylypiv <ipylypiv@google.com>]

On Mon, Jun 17, 2024 at 08:37:09AM +0900, Damien Le Moal wrote:
> On 6/15/24 04:18, Igor Pylypiv wrote:
> > Correct the ATA PASS-THROUGH fixed format sense data offsets to conform
> > to SPC-6 and SAT-5 specifications. Additionally, set the VALID bit to
> > indicate that the INFORMATION field contains valid information.
> > 
> > INFORMATION
> > ===========
> > 
> > SAT-5 Table 212 — "Fixed format sense data INFORMATION field for the ATA
> > PASS-THROUGH commands" defines the following format:
> > 
> > +------+------------+
> > | Byte |   Field    |
> > +------+------------+
> > |    0 | ERROR      |
> > |    1 | STATUS     |
> > |    2 | DEVICE     |
> > |    3 | COUNT(7:0) |
> > +------+------------+
> > 
> > SPC-6 Table 48 - "Fixed format sense data" specifies that the INFORMATION
> > field starts at byte 3 in sense buffer resulting in the following offsets
> > for the ATA PASS-THROUGH commands:
> > 
> > +------------+-------------------------+
> > |   Field    |  Offset in sense buffer |
> > +------------+-------------------------+
> > | ERROR      |  3                      |
> > | STATUS     |  4                      |
> > | DEVICE     |  5                      |
> > | COUNT(7:0) |  6                      |
> > +------------+-------------------------+
> > 
> > COMMAND-SPECIFIC INFORMATION
> > ============================
> > 
> > SAT-5 Table 213 - "Fixed format sense data COMMAND-SPECIFIC INFORMATION
> > field for ATA PASS-THROUGH" defines the following format:
> > 
> > +------+-------------------+
> > | Byte |        Field      |
> > +------+-------------------+
> > |    0 | FLAGS | LOG INDEX |
> > |    1 | LBA (7:0)         |
> > |    2 | LBA (15:8)        |
> > |    3 | LBA (23:16)       |
> > +------+-------------------+
> > 
> > SPC-6 Table 48 - "Fixed format sense data" specifies that
> > the COMMAND-SPECIFIC-INFORMATION field starts at byte 8
> > in sense buffer resulting in the following offsets for
> > the ATA PASS-THROUGH commands:
> > 
> > Offsets of these fields in the fixed sense format are as follows:
> > 
> > +-------------------+-------------------------+
> > |       Field       |  Offset in sense buffer |
> > +-------------------+-------------------------+
> > | FLAGS | LOG INDEX |  8                      |
> > | LBA (7:0)         |  9                      |
> > | LBA (15:8)        |  10                     |
> > | LBA (23:16)       |  11                     |
> > +-------------------+-------------------------+
> > 
> > Reported-by: Akshat Jain <akshatzen@google.com>
> > Fixes: 11093cb1ef56 ("libata-scsi: generate correct ATA pass-through sense")
> > Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
> > ---
> >  drivers/ata/libata-scsi.c | 26 +++++++++++++-------------
> >  1 file changed, 13 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> > index 4bfe47e7d266..8588512f5975 100644
> > --- a/drivers/ata/libata-scsi.c
> > +++ b/drivers/ata/libata-scsi.c
> > @@ -855,7 +855,6 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> >  	struct scsi_cmnd *cmd = qc->scsicmd;
> >  	struct ata_taskfile *tf = &qc->result_tf;
> >  	unsigned char *sb = cmd->sense_buffer;
> > -	unsigned char *desc = sb + 8;
> >  	u8 sense_key, asc, ascq;
> >  
> >  	if (qc->flags & ATA_QCFLAG_SENSE_VALID) {
> > @@ -880,8 +879,9 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> >  		scsi_build_sense(cmd, 1, RECOVERED_ERROR, 0, 0x1D);
> >  	}
> >  
> > -	if ((cmd->sense_buffer[0] & 0x7f) >= 0x72) {
> > +	if ((sb[0] & 0x7f) >= 0x72) {
> >  		u8 len;
> > +		unsigned char *desc;
> 
> Please move this declaration before the "u8 len" one.

Will do in v2. Could you please explain why this declaration order is preferred?

> Otherwise, this seems OK but needs a Cc: stable@vger.kernel.org tag added.

Ack, will add in v2.
> 
> >  
> >  		/* descriptor format */
> >  		len = sb[7];
> > @@ -919,21 +919,21 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> >  		}
> >  	} else {
> >  		/* Fixed sense format */
> > -		desc[0] = tf->error;
> > -		desc[1] = tf->status;
> > -		desc[2] = tf->device;
> > -		desc[3] = tf->nsect;
> > -		desc[7] = 0;
> > +		sb[0] |= 0x80;
> > +		sb[3] = tf->error;
> > +		sb[4] = tf->status;
> > +		sb[5] = tf->device;
> > +		sb[6] = tf->nsect;
> >  		if (tf->flags & ATA_TFLAG_LBA48)  {
> > -			desc[8] |= 0x80;
> > +			sb[8] |= 0x80;
> >  			if (tf->hob_nsect)
> > -				desc[8] |= 0x40;
> > +				sb[8] |= 0x40;>  			if (tf->hob_lbal || tf->hob_lbam || tf->hob_lbah)
> > -				desc[8] |= 0x20;
> > +				sb[8] |= 0x20;
> >  		}
> > -		desc[9] = tf->lbal;
> > -		desc[10] = tf->lbam;
> > -		desc[11] = tf->lbah;
> > +		sb[9] = tf->lbal;
> > +		sb[10] = tf->lbam;
> > +		sb[11] = tf->lbah;
> >  	}
> >  }
> >  
> 
> -- 
> Damien Le Moal
> Western Digital Research
>

Thank you,
Igor