RFC: complete rewrite of i2c-i801 for 2.6.x

Mark Studebaker mds4 at verizon.net
Wed Dec 8 04:01:32 CET 2004



Mark M. Hoffman wrote:
> Hi Mark:
> 
> (CCs trimmed)
> 
> * Mark D. Studebaker <mds4 at verizon.net> [2004-12-07 11:20:54 -0500]:
> 
>>My reading of the DB datasheet (in 2002 and now) is that it doesn't support a
>>standard i2c block read. The driver functionality bitmask reflects that.
>>I fixed the error message (which would only print out if a driver ignored 
>>the functionality mask).
> 
> 
> Interesting.  It looks like that datasheet only shows this:
> 
> 	S Addr Wr [A] Comm [A] D0 [A] D1 [A] S (read bytes...)
> 
> I agree that's not like any transaction we support.

correct. don't know what they were thinking.

> 
> OTOH, the ICH5 [1] datasheet shows this:
> 
> 	S Addr Wr [A] D1 [A] S (read bytes...)
> 
> That's exactly the transfer protocol that eeproms need, right?  (That's why I
> mentioned to Khali by IRC last weekend that I thought it should be possible.)
> 

I think it is what eeproms need (you omitted 'Addr' after the second 'S').
It matches what I wrote in doc/smbus-protocol in i2c
(that is, the i2c block functions are defined to take a 'command' byte, matching
 what eeproms need for 'random' reads and writes).

Does anybody have a ICH5/6? If so I can add support to the driver for testing.

mds


> It would be really bizarre if these two chipsets behaved differently in this
> respect - I wonder if the datasheets are correct?
> 
> [1] Well I just scanned all the other datasheets... only ICH5, ICH6, and
> 6300ESB appear to support the standard I2C block read.  Sorry Khali. :)
> 
> Regards,
> 



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