Re: [PATCH 16/22] libata: implement new SCR handling and port on/offline functions

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> Implement ata_scr_{valid|read|write|write_flush}() and
>>> ata_port_{online|offline}().  These functions replace
>>> scr_{read|write}() and sata_dev_present().
>>>
>>> Major difference between between the new SCR functions and the old
>>> ones is that the new ones have a way to signal error to the caller.
>>> This makes handling SCR-available and SCR-unavailable cases in the
>>> same path easier.  Also, it eases later PM implementation where SCR
>>> access can fail due to various reasons.
>>>
>>> ata_port_{online|offline}() functions return 1 only when they are
>>> affirmitive of the condition.  e.g.  if SCR is unaccessible or
>>> presence cannot be determined for other reasons, these functions
>>> return 0.  So, ata_port_online() != !ata_port_offline().  This
>>> distinction is useful in many exception handling cases.
>>
>> If its SATA-specific, it should have a "sata_" not "ata_" prefix.
>>
> 
> I thought about it but the 'S' in SCR stands for Serial ATA and we also 
> need to rename all PM functions to sata_pmp_xxx() - SCR and PMP are 
> already SATA specific.  Do you think that's the way to go?
> 
> For ata_port_on/offline(), I think it's better to leave them alone for 
> hotpluggable IDE hotbays with presence detection.

Yeah, I feel pretty strongly about the sata_ prefix, even for 
port_on/offline.  The implementation is purely SATA specific.

Should that ever change for sata_port_on/offline, it then becomes 
trivial to create a ->port_on/offline hook, and update all SATA drivers 
to pass sata_port_on/offline to it.  IOW, I think its unlikely that 
these functions, as implemented and used, will morph in the future from

	sata-port-on

to

	if (sata)
		sata-port-on
	else if (hotpluggable PATA bays)
		bay-on

Its much more likely we will create two separate functions for the 
separate functionality.  Thus, your ata_port_on will always be SATA 
specific, and deserving of the spiffy sata_ prefix.  And hey, we want to 
emphasize its SATA because SATA is cooler than PATA, too.

	Jeff