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

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Message-ID: <ac5a7cb9-7fd1-fb73-b872-d5a58846d99f@infradead.org>
Date:   Wed, 26 Aug 2020 11:06:22 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-i2c@...r.kernel.org
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-acpi@...r.kernel.org, Bingbu Cao <bingbu.cao@...el.com>,
        linux-media@...r.kernel.org,
        Chiranjeevi Rapolu <chiranjeevi.rapolu@...el.com>,
        Hyungwoo Yang <hyungwoo.yang@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rajmohan.mani@...el.com, Tomasz Figa <tfiga@...omium.org>,
        "Qiu, Tian Shu" <tian.shu.qiu@...el.com>
Subject: Re: [PATCH v6 6/6] Documentation: ACPI: Document
 allow-low-power-probe _DSD property

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@...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.
> +
> +How it works
> +============
> +
> +The property "allow-low-power-probe" boolean property may be used to tell Linux

Drop the first "property".

> +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
> +field and the "allow-low-power-probe" property is present, the device will not
> +be powered on for probe.

thanks.
-- 
~Randy