Status_byte() in drivers/scsi/scsi.h

Status_byte() in drivers/scsi/scsi.h

[Sachin Sant]

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.

Please let me know your thoughts.

Thanks
-Sachin

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

[Douglas Gilbert]

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

[Patch]Status_byte() in drivers/scsi/scsi.h

[Sachin Sant]

According to Dougs comments , here is the patch to include new macros
for SAM status codes . Patch is in drivers/scsi/scsi.h

--- scsi.h	2003-06-19 14:26:54.000000000 +0530
+++ scsi.h.new	2003-06-20 13:54:46.000000000 +0530
@@ -95,6 +95,13 @@
  *      host_byte   = set by low-level driver to indicate status.
  *      driver_byte = set by mid-level.
  */
+
+/* 
+ * Define a new macro sam_status_value for the status codes
+ * defined for new SCSI Architecture Model SAM 
+ */
+#define sam_status_value(scmd_result) ((scmd_result) & 0x7e)
+
 #define status_byte(result) (((result) >> 1) & 0x1f)
 #define msg_byte(result)    (((result) >> 8) & 0xff)

Any comments are welcome.

Thanks
-Sachin 
-----------------------------------------------------------------------------------

Douglas Gilbert wrote:
> 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
> 
> -
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Re: [Patch]Status_byte() in drivers/scsi/scsi.h

[James Bottomley]

On Fri, 2003-06-20 at 03:40, Sachin Sant wrote:
> 
> According to Dougs comments , here is the patch to include new macros
> for SAM status codes . Patch is in drivers/scsi/scsi.h
> 
> +#define sam_status_value(scmd_result) ((scmd_result) & 0x7e)

This is not the correct thing to do.  Our problems with the status byte
stem from its evolving meaning.  In SCSI-1, it was a bitmap, in SCSI-2 a
value in a bitrange of reserved bits and in SCSI-3 it covers an entire
byte.  In SAM-3 all the defined codes have bit zero set to zero, so your
current patch would do no harm for now, but bit zero is no-longer a
reserved bit.

James

Re: [Patch]Status_byte() in drivers/scsi/scsi.h

[Douglas Gilbert]

James Bottomley wrote:
> On Fri, 2003-06-20 at 03:40, Sachin Sant wrote:
> 
>>According to Dougs comments , here is the patch to include new macros
>>for SAM status codes . Patch is in drivers/scsi/scsi.h
>>
>>+#define sam_status_value(scmd_result) ((scmd_result) & 0x7e)
> 
> 
> This is not the correct thing to do.  Our problems with the status byte
> stem from its evolving meaning.  In SCSI-1, it was a bitmap, in SCSI-2 a
> value in a bitrange of reserved bits and in SCSI-3 it covers an entire
> byte.  In SAM-3 all the defined codes have bit zero set to zero, so your
> current patch would do no harm for now, but bit zero is no-longer a
> reserved bit.

SAM-3 (rev 7) doesn't say status is a byte either.
However since it doesn't define the endianess of
status then it is probably safe to assume it is.
If we choose a mask of 0xff we could only upset
SCSI-1 (and perhaps CCS) devices. Many of those
around?


On a related subject, SPC-3 defines a new "descriptor" sense
data format (see section 4.5). It is a lot cleaner and more
compact than the original one and is controlled by the D_SENSE
bit in the control mode page. Has anybody seen a target
that supports these?

Doug Gilbert

Re: [Patch]Status_byte() in drivers/scsi/scsi.h

[Jeff Garzik]

On Fri, Jun 20, 2003 at 11:52:39PM +1000, Douglas Gilbert wrote:
> On a related subject, SPC-3 defines a new "descriptor" sense
> data format (see section 4.5). It is a lot cleaner and more
> compact than the original one and is controlled by the D_SENSE
> bit in the control mode page. Has anybody seen a target
> that supports these?

If it's in the spec, I'm sure I could create one... <evil grin>

	Jeff