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SubjectOrder in "compatibility" DT property ignored by a platform bus
I was wondering how platform bus handles order of strings in the
"compatibility" property. After reading the code & testing it I
realized it doesn't.

The property should store strings ordered from the most specific to
the most generic. You could expect a more specific string to have a
priority while matching.

In platform_match there isn't any magic code for handling that. It
simply checks if a driver that was passed can support a given device.
I also did 2 quick tests with:
1) compatible = "foo", "bar";
2) compatible = "bar", "foo";
and it each case a foo platform driver was used. It just happened to
be before bar platform driver on kernel's internal list (both drivers
were built-in).

If you compare this with ARM's setup_machine_fdt you will notice that
one actually looks for the best matching machine code (it's handled
with the __of_match_node).

Am I correct understanding this isn't a proper behavior? Are there any
plans fixing this?
From what I can see a current design with the "match" callback doesn't
allow such a change, so I guess it'd need to be reworked first? Were
there any efforts regarding that?

--
Rafał

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