Re: [SCSI] Add support for braindead Cypress USB ATA passthrough CDBs

[James Bottomley <James.Bottomley@SteelEye.com>]

On Fri, 2005-12-23 at 11:12 -0800, David Caldwell wrote:
> > I think this approach is too invasive to the stack.  When this was
> > discussed in november, there wasn't much enthusiasm for resurrecting the
> > long dead LUN_INHIBIT flag.  The two suggested mechanisms are
> 
> Invasive because of the extra flag in the request structure?

Yes. But also having users determine this is wrong when it's a device
feature.

> > 2) If 1) doesn't work, then use a blacklist entry which the subsystems
> > would also have access to.
> 
> I think this might not be optimal. The problem is that it's impossible to 
> tell that it's a Cypress part from the USB side of things (or the SCSI side 
> for that matter), so there would have to be an entry for each of the 50,000 
> vendors of USB bridges.

I meant use it in the way usb uses other blacklist flags: set them from
slave_configure.

> What about the patch's cdb length additions in sg and scsi_lib.c? It seems 
> like half the code guesses CDB length and the other half passes it around. 
> Clearly, given devices like this, guessing isn't going to work 100% of the 
> time. So either eveyone needs to pass around lengths, or there needs to be 
> another flag somewhere. The code should at least be consistent though.

I don't think they're necessary, are they?  Zero in cmnd_len means
mid-layer determines size.  What it prevents is the issuing of vendor
specific commands via the API, which is arguably a good thing.

James