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[155.4.129.146]) by smtp.gmail.com with ESMTPSA id w24sm300041lfa.143.2021.06.09.03.02.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 03:02:02 -0700 (PDT) From: Ulf Hansson To: "Rafael J . Wysocki" , linux-pm@vger.kernel.org Cc: Ulf Hansson , Saravana Kannan , Alan Stern , Adrian Hunter , Tony Lindgren , Kevin Hilman , Geert Uytterhoeven , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 3/3] PM: runtime: Clarify documentation when callbacks are unassigned Date: Wed, 9 Jun 2021 12:01:57 +0200 Message-Id: <20210609100157.97635-1-ulf.hansson@linaro.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recent changes to the PM core allows ->runtime_suspend|resume callbacks to be unassigned. In the earlier behaviour the PM core would return -ENOSYS, when trying to runtime resume a device, for example. Let's update the documentation to clarify this. Signed-off-by: Ulf Hansson --- Changes in v3: - Fix spelling and further clarified the behaviour, according to comments from Alan. --- Documentation/power/runtime_pm.rst | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index 18ae21bf7f92..3d09c9fd450d 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -827,6 +827,14 @@ or driver about runtime power changes. Instead, the driver for the device's parent must take responsibility for telling the device's driver when the parent's power state changes. +Note that, in some cases it may not be desirable for subsystems/drivers to call +pm_runtime_no_callbacks() for their devices. This could be because a subset of +the runtime PM callbacks needs to be implemented, a platform dependent PM +domain could get attached to the device or that the device is power manged +through a supplier device link. For these reasons and to avoid boilerplate code +in subsystems/drivers, the PM core allows runtime PM callbacks to be +unassigned. + 9. Autosuspend, or automatically-delayed suspends ================================================= -- 2.25.1