On Mon, 2021-01-11 at 13:38 +0100, Matthias Brugger wrote:

Hi Matti,

On 11/01/2021 11:32, Vaittinen, Matti wrote:

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Hello Matthias & All,

On Mon, 2021-01-11 at 11:08 +0100, Matthias Brugger wrote:

quoted

On 11/01/2021 03:18, gene_chen(陳俊宇) wrote:

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[ Internal Use - External ]

Please don't top-post in the future.

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Hi Matthias,

I discussed OF match table with Mark in previous mail in our
PATCH
v3,
MFD should just instantiate the platform device.

Did you ever test that? Which MFD driver should instantiate the
device?
I had a look at mt6360-core.c (the obvious one) but I don't see
any
reference to
the regulator [1]. What am I missing?

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Mark Brown [off-list ref] 於 2020年8月20日 週四 下午7:45寫道：

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This device only exists in the context of a single parent
device, there
should be no need for a compatible string here - this is
just a
detail
of how Linux does things.  The MFD should just instntiate
the
platform
device.

Trying to autoload module without of_id_table will cause run-
time 
error:
ueventd: LoadWithAliases was unable to load
of:NregulatorT(null)Cmediatek,mt6360-regulator

You shouldn't have this described in the device tree at all,
like I
say
the MFD should just instantiate the platform device.

Well from my understanding the regulator has a device-tree entry
[2],
so it
needs to match against a device-tree node. My understanding is,
that
you need a
the devicetree node to describe the regulators provided by the
device. TBH I'm a
bit puzzled about the comment from Mark here. How does another DT
node be able
to reference a regulator if this is not described in DT? I think
we
need a DT
node here and the matching in the regulator and MFD driver to get
the
regulator
loaded via udev.

Others are better to answer - but as I spotted this from my inbox
I'll
give my 2 cents :) 

This can be done W/O regulators having own compatible. Please see
following:

drivers/mfd/rohm-bd718x7.c
drivers/regulator/bd718x7-regulator.c
Documentation/devicetree/bindings/mfd/rohm,bd71847-pmic.yaml
Documentation/devicetree/bindings/regulator/rohm,bd71847-
regulator.yaml

as example.

Thanks for the links. Yes that's' a way to go, but...

quoted

The device matching can be done via platform_device_id table.
I think the MODULE_ALIAS() is needed for module matching - but I
don't
remember without further code browsing.

Anyways, the BD71837/47/50 DT entry without compatible for
clk/regulators do probe and load the sub-devices.

As a "tradeoff" subdevices must retrieve the DT node from the
parent
device.

For my uneducated eyes the DT binding for regulators should be
changed.
Compatible should not be required and the example node should be
moved
to MFD binding document in the MFD node. But that's just my view on
this - not willing to push this to any direction!

Generally speaking, DT bindings are stable and can't be changed in a
none-compatible way. We could argue if there is any user of the
compatible out
there (probably there isn't any, as the code seems to not even be
working).

I think this depends on the device where driver(s) are used. Quite a
few devices allow updating the device-tree when SW is updated. But as I
said, I don't want to try pushing this one direction or other - I leave
it for those who have broader shoulders for pushing XD.

I was merely trying to answer your question :)

Best Regards
	Matti
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