On Wed, 27 Aug 2014, Oliver Neukum wrote:

> > I don't think we want to add another SCSI flag to say that READ
> > CAPACITY(10) is unreliable.
> 
> Why not? It would only be friendly to tell the upper layer
> of a malfunction if we know about it.

To what end?  What will the upper layer do with this information?

> > Given the difficulty of determining the true capacity, I see two
> > alternatives.  We could set the capacity to a ridiculously large value
> > (like 1 billion TB), or we could leave the capacity set to the low
> > value and disable the "block within bounds" checks.  Neither of these
> > is attractive and they both have issues of their own -- although the 
> > second is close to what Windows does.
> 
> That seems to be the most attractive solution to me.

I'm skeptical that you can convince the SCSI and block-layer developers 
about this.  Maybe they'll accept it if it is applied only to USB 
transports...

> > (For example, udev often tries to read the last sectors of a new drive, 
> > looking for a GPT or RAID signature.  That won't work if the capacity 
> > is set to some random value.)
> 
> Yes, but clipping has its own dangers. Suppose you use the medium
> without a partition table.

What would Windows do?  In the absence of a partition table, it would 
believe the value from READ CAPACITY, right?  Isn't that the same as 
clipping?

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Reply via email to