linux-kernel - Poulsbo I2C - /dev/i2c not seen when loading i2c-dev

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Date:	Thu, 31 Mar 2011 17:48:13 -0400
From:	simon@...gewell.org
To:	linux-input@...r.kernel.org
Cc:	"Jacob Pan" <jacob.jun.pan@...el.com>, linux-kernel@...r.kernel.org
Subject: Poulsbo I2C - /dev/i2c not seen when loading i2c-dev

Hi all,
I'm hoping that someone here can help. I am trying to get userland access
to the I2C bus(es) on an embedded system, however recent kernels (ie.
2.6.38) are not 'loading' any buses when I 'modprobe i2c-dev'.

Going back to 2.6.32 I am able to see 1 bus, and 'i2cdetect 0' shows a
single device sitting at address 0x69 (which I believe to EEPROM on the
wifi card... not confirmed).

The board is built around the Poulsbo and therefore using the 'i2c-isch'
driver.

Reviewing the schematic I see that there are several buses, each going to
individual components:
IT8516 U5/110+111 -> LTC1760 U6/18+22 [battery charger  0x1A/0x12]
IT8516 U5/115+116 -> W83L771 U60/8+7 [thermal sensor  0x18??]
IT8516 U5/117+118 -> LSM303DLH U64/19+20 [accel/compass  0x19]
POULSBO U2/G37+H38 -> PCI Express Socket

I am a little dismayed by the comment in 'i2c-isch.c' which suggest it can
handle only one i2c bus at any time.
--
/*
   Supports:
	Intel SCH chipsets (AF82US15W, AF82US15L, AF82UL11L)
   Note: we assume there can only be one device, with one SMBus interface.
*/
--

This seems to correlate to these comments:
http://www.linuxforums.org/forum/programming-scripting/175147-smbus-intel-sch-us15w.html

Can anyone confirm whether this is actually the case, and whether it is
possible to configure it to use a different controller address. One would
expect this to be a module option I guess, however it doesn't seem to take
any.

Many thanks in advance,
Simon.

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