Re: CFA 4.0 patch

[Sergei Shtylyov <sshtylyov@mvista.com>]

Hello.

On 15-05-2012 23:20, Andre Hedrick (anhedric) wrote:

> Sergei,

> Sorry wrong answer about broken devices, and if I had taken such short
> cuts in the past, the strength of the cheap storage would not have been
> there or present today in Linux.

> Just because someone calls it broken, because they don't read "ALL" the
> associated specification,

    Name the part I didn't read please.

> it means they don't understand what they don't know.

    From your words so far it follows to me that you who don't understand.

> So try again with all the information before the classic call if
> "it is broken" because I can't or don't know how to fix.

    Your fix is incorrect because it blindly assumes that device is CFA basing 
on word 0 while these alternate values (044Ah and 0040h) also correspond to 
hard disks. We can't make such decisions without consulting word 83 first 
which clearly follows from CFA 4.0. And in second of the identify data dumps 
you sent to me privately the device erroneously don't indicate CFA command set 
support in word 83, that's why it's not detected as CF. I agree however, that 
we shoiuld try and overcome this incompatibility by adding more heuristics but 
not in this proposed simplistic form.

> Cheers,
> Andre

> -----Original Message-----
> From: Sergei Shtylyov [mailto:sshtylyov@mvista.com]
> Sent: Tuesday, May 15, 2012 4:37 AM
> To: Andre Hedrick (anhedric)
> Cc: jgarzik@pobox.com; linux-ide@vger.kernel.org; lkml@vger.kernel.org
> Subject: Re: CFA 4.0 patch

> Hello.

> On 15-05-2012 8:57, Andre Hedrick (anhedric) wrote:

>> This is a missing part of the CFA 4.0 and above support.

>> 6.2.1.6.1 Word 0: General Configuration
>> 	This field indicates the general characteristics of the device.
>> When Word 0 of the Identify drive information is 848Ah then the device
>> is a CompactFlash Storage Card and complies with the CFA specification
>> and CFA command set. It is recommended that PC Card modes of operation
>> report only the 848Ah value as they are always intended as removable
>> devices.

>> Bits 15-0: CF Standard Configuration Value
>> Word 0 is 848Ah. This is the recommended value of Word 0.
>> 	Some operating systems require Bit 6 of Word 0 to be set to 1
>> (Non-removable device) to use the card as the root storage device. The
>> Card must be the root storage device when a host completely replaces
>> conventional disk storage with a CompactFlash Card in True IDE mode.
> To
>> support this requirement and provide capability for any future
> removable
>> media Cards, alternate handling of Word 0 is permitted.

>> Bits 15-0: CF Preferred Alternate Configuration Values

>> 044Ah: This is the alternate value of Word 0 turns on ATA device and
>> turns off Removable Media and Removable Device while 	preserving all
>> Retired bits in the word.

>> 0040h: This is the alternate value of Word 0 turns on ATA device and
>> turns off Removable Media and Removable Device while 	zeroing all
>> Retired bits in the word

>      If you did read a bit further, you'd have seen:

> Bit 15-12: Configuration Flag
> If bits 15:12 are set to 8h then Word 0 shall be 848Ah.
> If bits 15:12 are set to 0h then Bits 11:0 are set using the definitions
> below
> and the Card is
> required to support for the CFA command set and report that in bit 2 of
> Word 83.
> Bit 15:12 values other than 8h and 0h are prohibited.

>      That's why our code does what it does, and not checks for the
> alternate
> values. If our check in word 83 fails, we therefore have a broken
> device.

>> Cheers,
>> Andre
>> --------------------
>> The Linux X-ATA/SATA guy

>> --- linux-2.6.32.orig/include/linux/ata.h	Mon May 14 15:48:24 2012
>> +++ linux-2.6.32/include/linux/ata.h	Mon May 14 15:51:42 2012
>> @@ -819,6 +819,10 @@
>>    {
>>    	if (id[ATA_ID_CONFIG] == 0x848A)	/* Traditional CF */
>>    		return 1;
>> +	if (id[ATA_ID_CONFIG] == 0x044A)	/* Alternative CF w/
>> removable turned off, preserving retired bits */
>> +		return 1;
>> +	if (id[ATA_ID_CONFIG] == 0x0040)	/* Alternative CF w/
>> removable turned off, zeroing retired bits*/
>> +		return 1;
>>    	/*
>>    	 * CF specs don't require specific value in the word 0 anymore
>> and yet
>>    	 * they forbid to report the ATA version in the word 80 and
>> require the

MBR, Sergei