Subject: Re: "cell-index" vs. "index" vs. no index in I2C device nodes

From: Timur Tabi <[email-masked]>
Date: Thu, 05 Jun 2008 10:43:03 -0500

Grant Likely wrote:

> if you need explicit indexing then use an alias.  My opinion however
> is that explicit indexing is unnecessary and is just an artifact of
> current i2c subsystem internals.  There is already enough information
> in the device tree to match i2c devices with i2c busses without
> resorting to indexes.

Not for ALSA SoC V2 devices.  In ASoC V2, the "fabric" driver needs to identify
the codec by its specific I2C bus and address number.  The codec driver is not
an OF driver (normally), so it doesn't have access to any OF data.  It's just an
I2C driver, so its given an I2C address and some number that represents an adapter.

Therefore, the fabric driver and the codec driver need to independently
determine the I2C bus number, and they need to match.  The fabric driver parses
the OF tree and looks up the cell-index property.  The codec driver uses the
adapter->nr variable.  The patch I posted ensures that the two contain the same
number.

-- 
Timur Tabi
Linux kernel developer at Freescale