Re: Status_byte() in drivers/scsi/scsi.h

[Douglas Gilbert <dougg@torque.net>]

Sachin Sant wrote:
> There seems to be some problem with the status_byte( ) in scsi.h
> 
> A SAM status code SAM_STAT_TASK_ABORTED is ignored by status_byte() - it
> returns a status GOOD. If SAM status code SAM_STAT_TASK_ABORTED is set
> status_byte() must return 0x20.
> 
> In kernel file include/scsi/scsi.h new SCSI Architecture Model (SAM)
> Status Codes were presented as following:
> #define SAM_STAT_GOOD            0x00
> #define SAM_STAT_CHECK_CONDITION 0x02
> #define SAM_STAT_CONDITION_MET   0x04
> #define SAM_STAT_BUSY            0x08
> #define SAM_STAT_INTERMEDIATE    0x10
> #define SAM_STAT_INTERMEDIATE_CONDITION_MET 0x14
> #define SAM_STAT_RESERVATION_CONFLICT 0x18
> #define SAM_STAT_COMMAND_TERMINATED 0x22        /* obsolete in SAM-3 */
> #define SAM_STAT_TASK_SET_FULL   0x28
> #define SAM_STAT_ACA_ACTIVE      0x30
> #define SAM_STAT_TASK_ABORTED    0x40
> 
> This means that an implementation of a status_byte() function in
> drivers/scsi/scsi.h has to be changed from:
> 
>   #define status_byte(result) (((result) >> 1) & 0x1f)
> to:
>   #define status_byte(result) (((result) >> 1) & 0x3f)
> 
> Otherwise it would ignore a status code SAM_STAT_TASK_ABORTED and return
> GOOD.

Sachin,
The status_byte() macro is for SCSI-2 and earlier and
matches a Linux-specific set of defines that are
shifted from the "standard" values (e.g. CHECK_CONDITION).
In those days bit 6 was not in use.

We are still arguing about the exact form of the macro
to use that matches the SAM_STAT_ defines show above.
In the meantime you could use:
   #define sam_status_value(scmd_result) ((scmd_result) & 0x7e)
and compare the result with the SAM_STAT_ defines above.

Doug Gilbert