Re: [PATCH] remove ide-scsi

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

James Bottomley wrote:

>>>>    Oh, yes. SCSI emulation is just what Linux embedded world is asking 
>>>> for...
>>>>     
>>>>         
>>> Well ATAPI is SCSI emulation (its a sort of pidgin SCSI admittedly).
>>>   
>>>       
>>    ATAPI is SCSI transport (with maybe some quirks at SCSI command level 
>> tho, IIRC). ATA is neither thansport nor does it map to SCSI 1:1.
>>     
>
>
> Well, to be wholly accurate, since SCSI-3, SCSI has been separated into
> an architecture, primary command, device specific command and transport
> model (called the SCSI architecture model).

   Thanks, I'm well aware of all this. :-)
   My first encounter with SCSI dates back to 1993-94 -- it's a pity 
that I had to abandon this area (switching to that puny IDE ;-)...

> Starting with ATA-8, ATA
> will go this way again.

   It's gone that way in ATA/PI-7 actually, being broken into 3 separate 
documents then, one spoecifying the command set and 2 others PATA and 
SATA tranports.

>   What ATAPI actually is is a SCSI (really MMC
> for CD and SSC for tape)

   Unfortunately, the initial SFF documents specified both the transport 
protocol and the command sets (which somewhat diverged form what SCSI-2 
had, IIRC).
   Fortunately, once ANSI finally taken over ATAPI work, they dropped 
that stupid practice and started referring to MMC and SSC.

> command transported over ATA using the ATA
> PACKET command.  With ATA-8 it will be much more analogous to SCSI
> command over ATA transport.
>   

    I don't think "analogous" means that it will be sending SCSI CDBs 
over PATA/SATA is of native commands and turn ATA into ATAPI. So all 
this is fine but changes nothing about the SCSI emulation thing.

>> The code for emulating SCSI on ATA only burdens the kernel (and causes user 
>> complaints about changing disk names from /dev/hdx to /dev/sda :-).
>>     
>
> The code for sorting this out is already upstream in the block tree for
> 2.6.29.
>   

   Sorting out what, emulation?

   I have to cut my response short that that point. I must be totally 
crazy to allow myself to be dragged into this discussion having so much 
work to do... :-/

MBR, Sergei