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Date:   Tue, 12 Jan 2021 05:16:54 -0500
From:   Bill Mills <>
To:     Viresh Kumar <>
Cc:     Frank Rowand <>,
        Pantelis Antoniou <>,
        Rob Herring <>,,,,
        Vincent Guittot <>,, Masahiro Yamada <>
Subject: Re: [PATCH] of: unittest: Statically apply overlays using fdtoverlay

On 1/12/21 3:37 AM, Viresh Kumar wrote:
> On 11-01-21, 20:22, Bill Mills wrote:
>> On 1/11/21 5:06 PM, Frank Rowand wrote:
>>> NACK to this specific patch, in its current form.
>>> There are restrictions on applying an overlay at runtime that do not apply
>>> to applying an overlay to an FDT that will be loaded by the kernel during
>>> early boot.  Thus the unittest overlays _must_ be applied using the kernel
>>> overlay loading methods to test the kernel runtime overlay loading feature.
>>> I agree that testing fdtoverlay is a good idea.  I have not looked at the
>>> parent project to see how much testing of fdtoverlay occurs there, but I
>>> would prefer that fdtoverlay tests reside in the parent project if practical
>>> and reasonable.  If there is some reason that some fdtoverlay tests are
>>> more practical in the Linux kernel repository then I am open to adding
>>> them to the Linux kernel tree.
> I wasn't looking to add any testing for fdtoverlay in the kernel, but
> then I stumbled upon unit-tests here and thought it would be a good
> idea to get this built using static tools as well, as we aren't
> required to add any new source files for this and the existing tests
> already cover a lot of nodes.
> And so I am fine if we don't want to do this stuff in kernel.
>> I thought we were aligned that any new overlays into the kernel today would
>> only be for boot loader applied case.  Applying overlays at kernel runtime
>> was out of scope at your request.
>> Rob had requested that the overlays be test applied at build time.  I don't
>> think there is any way to test the kernel runtime method at build time
>> correct?
>> Please clarify your concern and your suggested way forward.
> The kernel does some overlay testing currently (at kernel boot only,
> not later), to see if the overlays get applied correctly or not, these
> are the unit tests.
> What Frank is probably saying is that the unit-tests dtbs shouldn't
> get used for testing fdtoverlay stuff. He isn't asking to support
> runtime application of overlays, but to not do fdtoverlay testing in
> the kernel.

Thanks Viresh, that makes sense.  Sorry for the confusion Frank.

Bill Mills

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