Re: [PATCH] megaraid_sas: Enable shared tag map

Christoph Hellwig
2014-10-02T09:19:21Z

On Thu, Oct 02, 2014 at 08:51:20AM +0200, Hannes Reinecke wrote:
>
> I'm afraid it's not _that_ easy.
> SCSI-II tagged queueing has some specific tag values:
>
> #define SIMPLE_QUEUE_TAG 0x20
> #define HEAD_OF_QUEUE_TAG 0x21
> #define ORDERED_QUEUE_TAG 0x22

These are not tag values. These are message codes set in the first byte
of the Queue tag message, the second byte is the actual tag.

> The recommendation here is to use 'scmd->request->tag' whenever
> you want to get to the tag number, and 'scmd->tag' if you have to
> play around with SCSI-II TCQ.
> But if not I would strongly advise to leave 'scmd->tag' alone.

Or kill off scmd->tag.. Let's see how feasible that is.