Re: [PATCH] 2.5 ide 48-bit usage

[Jens Axboe <axboe@suse.de>]

On Wed, May 07 2003, Linus Torvalds wrote:
> 
> On Wed, 7 May 2003, Jens Axboe wrote:
> > > 
> > > And testing. In particular, you might want to test whether a device 
> > > properly supports 48-bit addressing, either from the kernel or from user 
> > > programs.
> > 
> > For that, a forced 48-bit hwif->addressing inherited by drives will
> > suffice. And I agree, we should have that.
> 
> No no no.
> 
> You definitely do NOT want to set "hwif->addressing" to 1 before you've 
> tested whether it even _works_.

Well duh, of course not. Whether a given request is executed in 48-bit
or not is a check that _includes_ drive capabilities too of course.

> Imagine something like "hdparm" - other things are already in progress,
> the system is up, and IDE commands are potentially executing concurrently.  
> What something like that wants to do is to send one request out to check
> whether 48-bit addressing works, but it absolutely does NOT want to set 
> some interface-global flag that affects other commands.

Then it just puts a taskfile request on the request queue and lets it
reach the drive, nicely syncronized with the other requests. There's no
need to toggle any special bits for that.

> Only after it has verified that 48-bit addressing does work should it set 
> the global flag.

Sounds fine.

-- 
Jens Axboe