Hi everyone,

I have a similar question.
I'd like to "name" i2c devices so that a userspace application can 
somehow identify those devices with the same function across different 
boards (which may have different addresses or be connected to a 
different i2c bus, or be a physically different chip).

For instance "hwmon" devices get instantiated within sysfs under
/sys/class/hwmon/hwmonX

# cat /sys/class/hwmon/hwmon0/device/name
lm75

which I would like to be identified by the name "switch" (as in "switch 
temperature"). I was thinking about instantiating it as something like 
"lm75:switch" within i2c_board_info.type. For device-tree-less 
architectures, a trivial change within i2c_match_id() so to ignore the 
part following ":" seems to do the trick. Don't know about devicetree 
but I guess a similar approach could be imagined.

Another example would be given by EEPROMs: all boards are equipped with 
an EEPROM containing inventory management, which I would like to 
identify as "ivm". So something like "24c08:ivm".
After all, I'd like to be able to achive something like "named MTD 
partitions" which you can identify by looking at "/proc/mtd".

Maybe some other symbol could be used instead of ":", but anyhow, does 
the above make any sense at all to you?

Thanks a lot!
Gerlando

On 12/14/2012 09:38 PM, Grant Likely wrote:

On Tue, 11 Dec 2012 13:56:08 -0700, Stephen Warren[off-list ref]  wrote:

quoted

On 12/11/2012 01:21 PM, Olof Johansson wrote:

quoted

[+devicetree-discuss]

On Wed, Dec 5, 2012 at 2:36 PM, Peter Huewe[off-list ref]  wrote:

quoted

Hi,

I have a short question about the relations between i2c and devicetrees.

I was wondering
is the device part of the compatible string of a (trivial) i2c device
instanciated via devicetree _always_ identical to name in i2c_client.name ?
Or can it be somehow different?

It can be different, but the driver will then need to add a OF table
that matches the probing. By default the i2c/dt core code will strip
off the vendor prefix (before ",") and try probing with the rest of
the device name. If that doesn't match the client name, that is when
you need the additional table.

While relying on the prefix stripping works, I think I recall Grant
mentioning that people shouldn't rely on it - namely that any I2C device
that gets instantiated from DT should contain the OF match table
explicitly. I CC'd Grant in case I'm mis-quoting him.

I'm not quite that strict about it. The behaviour described above is
based merely on a heuristic but for a lot of drivers that don't do
anything special it works just fine. The moment you need to identify a
specific device it becomes better to use an of match table.

g.