Re: ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally attached PHYs)

Stefan Richter
2005-10-22T09:29:47Z

Jeff Garzik wrote:
> Luben Tuikov wrote:
>>>>> Examples are DMA boundary and s/g limit,
>>>>> among others. When confronted with this, you proposed an
>>>>> additional hardware information struct which duplicates
>>>>> Scsi_Host_Template.
>>>>
>>>> I told you -- I have this in the struct asd_ha_struct and it was merely
>>>> a downplay that I didn't include the same thing in struct
>>>> sas_ha_struct.
>>
>> Here is the commit in question:
>> http://linux.adaptec.com/sas/git/?p=linux-2.6-sas.git;a=commit;h=785747ddc631f7618d728a377346965f7db2256a
>
> This effectively illustrates the wrong thing to do: duplicating
> information that's already in Scsi_Host_Template.
>
> Just use Scsi_Host_Template in the LLDD and see where that goes.

Will cmd_per_lun, sg_tablesize, max_sectors, dma_boundary,
use_clustering ever have to be adjusted specifically for a SAS hardware?

Obviuosly none of this is required _at the moment_. IOW neither the
introduction of a sas_ha_hw_profile nor a pass-through of
scsi_host_template down to SAS interconnect drivers is required right
now. So why do one or the other now? Isn't it a sensible rule to not
solve problems now which do not exist yet?

(I guess Luben only introduced sas_ha_hw_profile to demonstrate that
there will never be an absolute requirement for scsi_host_template ---
in its present form --- to be visible in a SAS transport layer <-> SAS
interconnect driver interface. And there are certainly more alternatives
to these two approaches.)
--
Stefan Richter
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