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

Tejun Heo
2006-07-31T18:52:10Z

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