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Date:   Mon, 8 Mar 2021 08:50:48 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Zhang Rui <rui.zhang@intel.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>
Subject: Re: driver notification when switching between battery vs AC power?
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On Sun, Mar 07, 2021 at 09:53:06PM +0800, Zhang Rui wrote:
> Thanks for adding me in the loop.
> 
> Yes, an ACPI notifier callback should be sufficient for this purpose.
> 
> Usually, we get an ACPI notification upon AC plug/unplug, so what we
> need in the NVMe driver is to get the notification and then get the
> status of AC adapter. As ACPI AC driver always sends the AC events to
> acpi notifier chain, what we need is 
> a) define a notifier callback, and in the notifier callback
>    1. ignore non-AC devices,
>    2. get AC status, you can refer to acpi_ac_get_state()
> b) register the notifier cb to ACPI notifier chain, by invoking
>    register_acpi_notifier()

Not my direct priority now, but would there be any objections to
wire up a power_source_notifier method in struct dev_pm_ops to
avoid boilerplate code and ACPI dependencies in drivers?