SCSI synchronization and error handling

SCSI synchronization and error handling

[Jeff Garzik]

I'm doing some more work on my scsi LLD, libata, and have a few 
questions for the experts in the crowd.

In ATA, some commands need to be sent when no other commands are queued 
to hardware.  Let's say I have a command stream that looks like

	queued write
	queued read
	queued read
	queued write
	non-queued SMART command
	queued write
	queued write

What's the best way to ensure that the SMART command is only executed 
after preceding, queued commands are completed?  My guess is to return 
MLQUEUE_BUSY if (a) ->queuecommand is passed a non-queued command AND 
(b) there are commands queued to hardware already.

Re: SCSI synchronization and error handling

[James Bottomley]

On Wed, 2004-06-30 at 14:43, Jeff Garzik wrote:
> What's the best way to ensure that the SMART command is only executed 
> after preceding, queued commands are completed?  My guess is to return 
> MLQUEUE_BUSY if (a) ->queuecommand is passed a non-queued command AND 
> (b) there are commands queued to hardware already.

So you have to quiesce the device before issuing the smart command?  In
which case, scsi_quiesce_device() is the API you want.  Or is this some
type of command ordering problem you're trying to solve?

James