Re: SATA "target mode" (or "Channel-to-Channel" comm mode)

[Mark Lord <liml@rtr.ca>]

Jeff Garzik wrote:
> Mark Lord wrote:
>> Jeff Garzik wrote:
..
>>> The miscdev (i.e. chrdev) interface found in 
>>> drivers/scsi/scsi_tgt_if.c of repo [1] seems pretty generic, simple, 
>>> small and applicable to portions of the problem presented here...  
>>> The basic task in scsi_tgt_if's case is just shoveling packets 
>>> to/from userspace.
>> ..
>>
>> Except it's rather SCSI specific, and the userspace frontend even more so.
>> The code expects a SCSI command block, LUN, TAG, and other fields that
>> a SATA FIS won't have.  Seems clumsy, particularly when we (in theory)
>> are trying to decouple libata from SCSI.   But if that's the way,
>> then I can clumsily wrap each FIS in a fake ATA_16 header or something.
> 
> The kernel bits are not terribly SCSI-specific.  I'd ignore the userland 
> bits.
> 
> We just have to get the interface right.  Even if we "cp scsi_tgt_if.c 
> ata_tgt_if.c" and then go from there, we should make an effort to create 
> similar packet push/pull interfaces.
..

Yeah, that does look like a good starting point.
To begin with, I'll see if I can just wrap the SATA FIS+data
into something that scsi_tgt_if.c will pass through unmolested.

This will give us a way to play with it in the 2.6.30 time frame,
and we can fork it or tweak it as needed for later releases then.

> Creating something wildly different would be counterproductive.
..

Yes we definitely should re-use that stuff if possible.
I think it all feeds to/from netlink, too, though it's been
a month since I last tried to find my way through it all.

Patches in a week or so.

Cheers