On Thu, 06 Dec 2012, Viresh Kumar wrote:

On 6 December 2012 15:20, Lee Jones [off-list ref] wrote:

quoted

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But regardless, it is the responsiblity of the probe function to go and
look if of_driver_match_device() matches against anything if it cares
about the of_match_table entries (for instance, if there is extra data
attached).

Ok, so filling .data field in of_device_id[] is not required for our case as
we aren't doing anything special in our drivers.

This is exactly my point, and the reason I bought it up in the
first place. Normally when you specify an ID table and populate
the .data attribute, you parse for it in the code and then cast
it back to some kind of useful data. However, you're not doing
that, which is precisely why I wondered if the table was
necessary at all. In all my testing, the DT portion worked and
the correct STMPE chip was identified without it.

Probably Vipul (Author of this patch), copied it from existing i2c/spi
clients, which have also added this blindly :)

quoted

So, are you adding the table for good reason, or because you
think it's the right thing to do?

I would be keeping the table as that's the right thing to do. 

So then I'm back to my original question, why?

What is it used for? What difference does it make?

I could understand if the .data attribute was used in the driver
to make vital decisions based on STMPE version, but it's not. So
why are we burdening the driver with unused code that's not
required? Other than to get your mainlined patch-count up of
course? This has an air of "placing header files in alphabetical
order" about it. ;)

By chance
our non-DT and DT tables had a difference of "st," only in the name
of instances and so it worked without tables. Otherwise it couldn't
have worked.

Over that, i am looking to bring the "stmpe,id" binding back again (unless
you have a better option), as device name is not coming from DT currently,
which we discussed earlier.

Or you could not put unnecessary bindings into the Device Tree
by putting two and two together and realise that using the table
is the correct thing to do instead. This actually gives reason
to you previous patch, but should probably be fixed-up into it
so it has some proper meaning/purpose. ;)

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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