linux-kernel - Re: [PATCH v7 6/6] Documentation: ACPI: Document allow-low-power-probe

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Message-ID: <20200902195939.GG32646@paasikivi.fi.intel.com>
Date:   Wed, 2 Sep 2020 22:59:39 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     linux-i2c <linux-i2c@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Mani, Rajmohan" <rajmohan.mani@...el.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Chiranjeevi Rapolu <chiranjeevi.rapolu@...el.com>,
        Hyungwoo Yang <hyungwoo.yang@...el.com>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v7 6/6] Documentation: ACPI: Document
 allow-low-power-probe _DSD property

On Wed, Sep 02, 2020 at 06:34:30PM +0200, Rafael J. Wysocki wrote:
> On Wed, Sep 2, 2020 at 6:31 PM Sakari Ailus
> <sakari.ailus@...ux.intel.com> wrote:
> >
> > Hi Rafael,
> >
> > Thank you for the review.
> >
> > On Wed, Sep 02, 2020 at 05:57:01PM +0200, Rafael J. Wysocki wrote:
> > > On Tue, Sep 1, 2020 at 11:03 PM Sakari Ailus
> > > <sakari.ailus@...ux.intel.com> wrote:
> > > >
> > > > Document the probe-low-power _DSD property and how it is used with I²C
> > > > drivers.
> > >
> > > I would reorder the series to make this go right after the [1/6] or
> > > maybe even fold it into that patch.
> > >
> > > The point is that the changes in [1/6] clearly depend on the property
> > > defined here.
> >
> > Ack.
> >
> > >
> > > > Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
> > > > ---
> > > >  .../acpi/dsd/allow-low-power-probe.rst        | 28 +++++++++++++++++++
> > > >  Documentation/firmware-guide/acpi/index.rst   |  1 +
> > > >  2 files changed, 29 insertions(+)
> > > >  create mode 100644 Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst
> > > >
> > > > diff --git a/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst b/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst
> > > > new file mode 100644
> > > > index 0000000000000..6fcc89162b898
> > > > --- /dev/null
> > > > +++ b/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst
> > > > @@ -0,0 +1,28 @@
> > > > +.. SPDX-License-Identifier: GPL-2.0
> > > > +
> > > > +======================================
> > > > +Probing I²C devices in low power state
> > > > +======================================
> > > > +
> > > > +Introduction
> > > > +============
> > > > +
> > > > +In some cases it may be preferred to leave certain devices powered off for the
> > > > +entire system bootup if powering on these devices has adverse side effects,
> > > > +beyond just powering on the said device. Linux recognizes the _DSD property
> > > > +"allow-low-power-probe" that can be used for this purpose.
> > >
> > > It would be good to refer to the document defining the generic _DSD
> > > properties mechanism and the GUID used for that from here.
> >
> > I'll add a reference to the device properties UUID for _DSD spec.
> >
> > >
> > > The meaning of  "_DSD property" may not be entirely clear to the
> > > reader as it stands.
> > >
> > > And maybe call the property "i2c-allow-low-power-probe" or similar, to
> > > indicate that it is specific to i2c.
> >
> > The bus determines that already, and it's only defined for I²C here. Should
> > we need this in the future for e.g. I3C, there would be no need to think of
> > renaming it, just changing the documentation and implementation.
> >
> > I don't have a strong opinion on that though.
> 
> The point is that the property is not going to be recognized beyond i2c.

Not right now, that is true. Sure, I can change it for v8.

-- 
Sakari Ailus