Re: [PATCH 2/3] SCSI core and sd: early detection of medium not present

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

On Fri, 2006-06-09 at 10:13 -0400, Alan Stern wrote:
> I did it that way in the patch because it was the only simple choice.  The 
> scsi_test_unit_ready() routine is part of the SCSI core and can be called 
> for devices that aren't disks.  Hence any flag it sets cannot be part of 
> the scsi_disk structure.

The slightly more complex choice that would be to extend
scsi_test_unit_ready() to allow the sending of a sense header pointer.
Then any user could use the sense return data for setting local
flags ... and thus, they could be kept local.

> In principle the information could be conveyed in the return value from 
> scsi_test_unit_ready() rather than in a static flag.  But the routine has 
> several callers and I didn't want to change all of them to recognize a 
> -ENOMEDIUM return code.  Now in the long run, perhaps that would be a good 
> thing to do.  Or perhaps moving the flag to scsi_device would be better, I 
> don't know...
> 
> Ultimately this boils down to how you want to represent "No medium 
> present" in the SCSI core.  What do you think is the bets way?

Well ... that's where I think we follow the CD people, since they're the
ones who have this occurring the most often.

James