On Mon, Sep 11, 2017 at 03:34:16PM +0200, Hans Verkuil wrote:

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+		u32 val;
+
+		fwnode_for_each_child_node(fwnode, child) {
+			if (fwnode_property_read_u32(child, *props, &val))
+				continue;
+
+			if (val == *args)
+				break;

I'm lost. This really needs comments and perhaps even an DT or ACPI example
so you can see what exactly it is we're doing here.

I'll add comments to the code. A good example will be ACPI documentation
for LEDs, see 17th patch in v9. That will go through the linux-pm tree so
it won't be available in the same tree for a while.

Ideally an ACPI and an equivalent DT example would be nice to have, but I might
be asking too much. I'm not that familiar with ACPI, so for me a DT example
is easier.

This won't be useful on DT although you could technically use it. In DT you
can directly refer to any node but on ACPI you can just refer to devices,
hence this.

So this function will effectively only be used with acpi? That should be
documented. I think that explains some of my confusion since I was trying
to map this code to a device tree, without much success.

I'll add to the documentation of the function:

 * While it is technically possible to use this function on DT, it is only
 * meaningful on ACPI. On Device tree you can refer to any node in the tree but
 * on ACPI the references are limited to devices.

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Would you be happy with the leds.txt example? I think it's a good example
as it's directly related to this.

Yes, that will work.

I'll add a separate patch that I'll post later on. The ACPI documentation
should get merged first.

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi