Re: [PATCH] libata ATA vs SATA detection and workaround.

[Jeff Garzik <jgarzik@pobox.com>]

Brad Campbell wrote:
> 
>> I'm still pondering what Alan was hinting at, a bit.  You (Brad) are 
>> correct in pointing out that this code should only trigger for the 
>> correct situations (lba48, etc.) which are only present on modern 
>> drives, but...  there is still a chance that word 93 will be zero on 
>> some weird (probably non-compliant) device.
> 
> 
> I agree completely, though my feeling is that if someone plugs a device 
> that broken into a SATA controller via a bridge then there "aint nuffin 
> we can do about it" anyway and if it breaks it breaks. I guess we could 
> offer the option you suggested before where we load the individual 
> drivers as modules and provide a "knobble" module parm that will limit 
> max_sectors to 200 and udma_mask to udma/100.
> Then we get the hassle if someone wants to use it as the root device, 
> but I guess then you move to an initrd and load the module from there.
> 
> How far do we want to take it?

For now I think moving your code to ata_dev_config() function is 
sufficient, with one modification:

Move the
	((ap->cbl == ATA_CBL_SATA) && (!ata_id_is_sata(ap->device)))
test into a separate function all its own, "ata_knobble_device" or 
somesuch.  static inline if you wish.

Then it will be trivial to add a 'knobble' module parm later on, by 
simply modifying ata_knobble_device() to also check the module parameter 
in addition to the existing tests.

	Jeff