Re: [PATCH 1/2] em28xx: allow setting the eeprom bus at cards struct

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On Mon, May 1, 2017 at 10:11 AM, Frank Schäfer
<fschaefer.oss@xxxxxxxxxxxxxx> wrote:
>
> Am 01.05.2017 um 13:38 schrieb Mauro Carvalho Chehab:
>> Right now, all devices use bus 0 for eeprom. However, newer
>> versions of Terratec H6 use a different buffer for eeprom.
>>
>> So, add support to use a different I2C address for eeprom.
>
> Has this been tested ?
> Did you read my reply to the previous patch version ?:
> See http://www.spinics.net/lists/linux-media/msg114860.html
>
> I doubt it will work. At least not for the device from the thread in the
> Kodi-forum.

Based on what I know about the Empia 2874/2884 design, I would be
absolutely shocked if the eeprom was really on the second I2C bus.
The boot code in ROM requires the eeprom to be on bus 0 in order to
find the 8051 microcode to be executed.  This is a documented hardware
design requirement.

I have seen designs where the first bus is accessible through an I2C
gate on a demodulator on the second bus.  This creates a multi-master
situation and I have no idea why anyone would ever do this.  However
it does explain a situation where the EEPROM could be optionally
accessed via the second bus (if the I2C gate on the demod was open at
the time).

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com




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