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

From: Tejun Heo
Date: Mon Jul 31 2006 - 14:49:56 EST


Alan Cox wrote:
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

primary port already stolen by drivers/ide secondary port free

legacy_mode = ATA_PORT_SECONDARY

port_num = 0
hard_port_num = 1


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?

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