Re: VESA, EDID & flat panels

["Antonino A. Daplas" <adaplas@gmail.com>]

Benjamin Herrenschmidt wrote:
>> It think it's because the (basic) EDID is retrieved with (basic) DDC
>> (address 0x50).  If I'm not mistaken, E-EDID is retrieved with E-DDC
>> (address 0xa0). I don't exactly know the protocol (E-DDDC specs are not
>> freely available), but try probing your i2c busses with:
>>
>> i2cdump 0,1,2,etc 0xa0 
>>
>> and see if you get anything.
> 
> Are you sure we aren't talking about the same address here ? Address
> 0xa0 _is_ 0x50 shifted one bit left ... (The low bit of an i2c address
> is the RW bit). i2cdump takes shifted addresses, thus you can't pass it
> anything above 0x7f, thus passing it 0x50 is what gives you address
> 0xa0 :)
> 
> Ben.
> 
> 
> 

Here's a snippet from the HDMI specs. Not sure how helpful this is

"8.4.3 Segment pointer
 Enhanced DDC allows access of up to 32 Kbytes of data. This is accomplished
 using a combination of the 0xA0/0xA1 address pair and a segment pointer. For
 each value of the segment pointer, 256 bytes of data are available at the
 0xA0/0xA1 address pair. An unspecified segment pointer references the same
 data as when the segment pointer is zero. Each successive value of the
 segment pointer allows access to the next two blocks of E-EDID (128 bytes
 each). The value of the segment pointer register cannot be read since it is
 reset at the completion of each command."

Tony



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