Re: [PATCH] ide/libata: fix ata_id_is_cfa()

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Alan Cox wrote:

>> totally wrong in that part from the very start -- CF devices don't report ATA 
>> standard support in word 80, that's forbidden (!) by the CF specs since at 
>> least 2.1.
>>     
>
> And the ATA world says that if word 80 doesn't report any standards then
> the word is potentially undefined....welcome to PC hell
>
> Perhaps the best we can do is to test
>
> 	word 80 == 0 && word 83 bit set && word 83 valid
>
> Fortunately the use is almost entirely to print the right CFA/ATA string
> at boot ?
>   

    There was intent to use it for filtering out DMA modes on incapable 
CF slots, for the lack of better criterion -- these slots usually has a 
master/slave switch connected, so can't be tied to the drive #, only to 
the channel # and the board's DMI ID.

> Now Sergei if you'd said that explicitly (or if you did before I didn't
> see it) it would have been a bit simpler to work out why you were arguing
> the needed for these changes.
>   

   I was arguing entirely out of thinking that the version check is not 
really needed. The fact that CF spec. forbids reporting it was a 
surprise to me as well.

> Alan
>   

MBR, Sergei