linux-kernel - Re: [PATCH v2] treewide: Fix instantiation of devices in DT overlays

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Message-ID: <CAMuHMdXSn=OuRWcQ08buh7F7Rqbn_hNSB9hpSLQTAvX=EYtFVw@mail.gmail.com>
Date:   Wed, 29 Mar 2023 18:49:59 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Wolfram Sang <wsa@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] treewide: Fix instantiation of devices in DT overlays

Hi Frank,

On Wed, Mar 29, 2023 at 6:06 PM Frank Rowand <frowand.list@...il.com> wrote:
> On 3/24/23 04:30, Geert Uytterhoeven wrote:
> > When loading a DT overlay that creates a device, the device is not
> > instantiated, unless the DT overlay is unloaded and reloaded again.
>
> Can you elaborate on why this is?  What the relevant code paths are?

Honestly, I don't know.

>From my local quotes collection:

   "There are two ways of constructing a software design.
    One way is to make it so simple that there are obviously no deficiencies.
    And the other way is to make it so complicated that there are no obvious
    deficiencies."
                                           -- C.A.R Hoare

The double hierarchies of DT and fw_devlink are just too complicated...

> > Saravana explains:
> >   Basically for all overlays (I hope the function is only used for
> >   overlays) we assume all nodes are NOT devices until they actually
> >   get added as a device.
> >
> > Based on a patch by Saravana Kannan, which covered only platform and spi
> > devices.
>
> > Fixes: 4a032827daa89350 ("of: property: Simplify of_link_to_phandle()")
>
> From a quick scan of the fixed commit, I don't see how that commit caused the problem.
> Can you give a quick clue?  (The clue does not need to be added to the commit message,
> but please at least put it below the "---" if there are additional versions of this
> patch.)

I bisected the issue to that commit. Reverting the commit fixed the
issue for me.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds