Re: [PATCH v4] libata: Add hwmon support for SMART temperature sensors

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2018-09-13 at 16:22 +0200, Linus Walleij wrote:
[...]
> +	/* Send ATA command to read SMART values */
> +	memset(scsi_cmd, 0, sizeof(scsi_cmd));
> +	scsi_cmd[0] = ATA_16;
> +	scsi_cmd[1] = (4 << 1); /* PIO Data-in */
> +	/*
> +	 * No off.line or cc, read from dev, block count in sector
> count
> +	 * field.
> +	 */
> +	scsi_cmd[2] = 0x0e;
> +	scsi_cmd[4] = ATA_SMART_READ_VALUES;
> +	scsi_cmd[6] = 1; /* Read 1 sector */
> +	scsi_cmd[8] = 0; /* args[1]; */
> +	scsi_cmd[10] = ATA_SMART_LBAM_PASS;
> +	scsi_cmd[12] = ATA_SMART_LBAH_PASS;
> +	scsi_cmd[14] = ATA_CMD_SMART;
> +
> +	cmd_result = scsi_execute(ata->sdev, scsi_cmd,
> DMA_FROM_DEVICE,
> +				  buf, ATA_SECT_SIZE,
> +				  NULL, &sshdr, 10 * HZ, 5, 0, 0,
> NULL);

Given that you're using scsi_execute and this would work on most SAS
drives as well as SATA ones, why not use the SAS mode pages and we'll
translate it to SATA in the existing libata-scsi SAT?

That way this can work on all SCSI devices that support SMART not just
the SATA subset.

If you can't figure out how to do this initially, then simply
separating smart from libata is a good first start so we can build on
it in SCSI as well.

James