Re: [PATCH v6 6/6] Documentation: ACPI: Document allow-low-power-probe _DSD property

From: Sakari Ailus <sakari.ailus@iki.fi>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>,
	linux-i2c@vger.kernel.org, Wolfram Sang <wsa@the-dreams.de>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	linux-acpi@vger.kernel.org, Bingbu Cao <bingbu.cao@intel.com>,
	linux-media@vger.kernel.org,
	Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>,
	Hyungwoo Yang <hyungwoo.yang@intel.com>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-kernel@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	rajmohan.mani@intel.com, Tomasz Figa <tfiga@chromium.org>,
	"Qiu, Tian Shu" <tian.shu.qiu@intel.com>
Subject: Re: [PATCH v6 6/6] Documentation: ACPI: Document allow-low-power-probe _DSD property
Date: Tue, 1 Sep 2020 23:28:55 +0300	[thread overview]
Message-ID: <20200901202854.GA4392@valkosipuli.retiisi.org.uk> (raw)
In-Reply-To: <20200827132822.GI24582@paasikivi.fi.intel.com>

On Thu, Aug 27, 2020 at 04:28:22PM +0300, Sakari Ailus wrote:
> On Wed, Aug 26, 2020 at 11:06:22AM -0700, Randy Dunlap wrote:
> > On 8/26/20 4:54 AM, Sakari Ailus wrote:
> > > Document the probe-low-power _DSD property and how it is used with I²C
> > > drivers.
> > > 
> > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.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.
> > > +
> > > +How it works
> > > +============
> > > +
> > > +The property "allow-low-power-probe" boolean property may be used to tell Linux
> > 
> > Drop the first "property".
> > 
> 
> Thanks, will fix for v7.
> 
> > > +that the I²C framework should instruct the kernel ACPI framework to leave the
> > > +device in the low power state. If the driver indicates its support for this by
> > > +setting the I2C_DRV_FL_ALLOW_LOW_POWER_PROBE flag in struct i2c_driver.flags
> 
> This is leftover from v5 actually, I'll change the documentation to mention
> the allow_low_power_probe as well.

Hmm. It seems I ended up sending the set with the flags field.

I'll keep it as-is if that's okay...

-- 
Sakari Ailus