Re: [2.6.18-rc2-mm1] libata ate one PATA channel

[Tejun Heo]

Hello,

Alan Cox wrote:
[--snip--]
> > I killed hard_port_no by s/ap->hard_port_no/ap->port_no/g without 
> > actually reviewing the usages (man, those are a LOT).  If all pata 
> > drivers always relied on ap->hard_port_no representing the actual port 
> > index in the controller, there shouldn't be a problem.  But, just in 
> > case, please review the change.
>
> Think about the following execution sequence
>
> ati_pci_init_one
> 	primary port already stolen by drivers/ide 
> 	secondary port free
>
> 	legacy_mode = ATA_PORT_SECONDARY
> 	ata_pci_init_legacy_port
>
> 	port_num = 0
> 	hard_port_num = 1
>
> 	*kerunnccchhhhhh*

Ah... You're right.  That will make port_no different from the hw port#.

> > If this fixes Magallon's problem and you agree with the fix, I'll break 
> > it down to two patches and submit'em to you with proper heading and all.
>
> I agree with the theory and the diagnosis. I'm a bit worried about
> hard_port_no however and I don't think that bit is safe in the secondary
> only corner case. Registering both always and disabling one works for me
> as a cleanup.
>
> If you do that then I'll audit all the drivers use of ->port_no against
> the patches.

I like 'registering both always and disabling one' approach for 
partially stolen legacy devices.  We can make ->hard_port_no do the job 
as before, but IMHO it's error-prone and only useful for very limited 
cases (first legacy port stolen).

Jeff, what do you think?

--
tejun
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