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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Tue, 2 Nov 2021 22:26:39 +0200
Message-ID: <CAHp75Vfo0Bp5SCeb1_oKa5BZBj=X9KdDicbVpUyR4HKY_MDsqg@mail.gmail.com>
Subject: Re: [RFC PATCH] software node: Skip duplicated software_node sysfs
To:     Qian Cai <quic_qiancai@quicinc.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Nov 2, 2021 at 10:20 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Tue, Nov 2, 2021 at 9:44 PM Qian Cai <quic_qiancai@quicinc.com> wrote:
> > On 11/1/21 7:51 PM, Andy Shevchenko wrote:
> > > No, it=E2=80=99s not so easy. What you are doing is a papering over t=
he real issue
> > > which is the limitation of the firmware nodes to two. What we need is=
 to
> > > drop the link from struct fwnode_handle, move it to upper layer and m=
odify
> > > all fwnode ops to be used over the list of fwnode:s.
> >
> > Andy, this is my first time touching fwnode/swnode. After reading the
> > source code for a few hours, I still don't understand the hint here.
> > Specifically, what does the "the link" refer to?
>
> https://elixir.bootlin.com/linux/latest/source/include/linux/fwnode.h#L36
>
> (Property related) fwnode (as of today) is the single linked list with
> only two possible entries. Comments against set_primary_fwnode()
> followed by set_secondary_fwnode() may shed a bit of light here
> https://elixir.bootlin.com/linux/latest/source/drivers/base/core.c#L4724

What you can start with, btw, is adding the trace events / points to
these two functions. (Currently only devres is enabled:
https://elixir.bootlin.com/linux/latest/source/drivers/base/trace.h)

When you do this, you may actually see what's going on and how the
swnode tries to recreate the same file.

--=20
With Best Regards,
Andy Shevchenko