linux-kernel - [PATCH] platform/surface: aggregator: Fix warning when controller is destroyed in probe

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Message-ID: <20240811124645.246016-1-luzmaximilian@gmail.com>
Date: Sun, 11 Aug 2024 14:46:44 +0200
From: Maximilian Luz <luzmaximilian@...il.com>
To: Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Maximilian Luz <luzmaximilian@...il.com>,
	platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] platform/surface: aggregator: Fix warning when controller is destroyed in probe

There is a small window in ssam_serial_hub_probe() where the controller
is initialized but has not been started yet. Specifically, between
ssam_controller_init() and ssam_controller_start(). Any failure in this
window, for example caused by a failure of serdev_device_open(),
currently results in an incorrect warning being emitted.

In particular, any failure in this window results in the controller
being destroyed via ssam_controller_destroy(). This function checks the
state of the controller and, in an attempt to validate that the
controller has been cleanly shut down before we try and deallocate any
resources, emits a warning if that state is not SSAM_CONTROLLER_STOPPED.

However, since we have only just initialized the controller and have not
yet started it, its state is SSAM_CONTROLLER_INITIALIZED. Note that this
is the only point at which the controller has this state, as it will
change after we start the controller with ssam_controller_start() and
never revert back. Further, at this point no communication has taken
place and the sender and receiver threads have not been started yet (and
we may not even have an open serdev device either).

Therefore, it is perfectly safe to call ssam_controller_destroy() with a
state of SSAM_CONTROLLER_INITIALIZED. This, however, means that the
warning currently being emitted is incorrect. Fix it by extending the
check.

Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem")
Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>
---
 drivers/platform/surface/aggregator/controller.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/surface/aggregator/controller.c b/drivers/platform/surface/aggregator/controller.c
index 7fc602e01487..7e89f547999b 100644
--- a/drivers/platform/surface/aggregator/controller.c
+++ b/drivers/platform/surface/aggregator/controller.c
@@ -1354,7 +1354,8 @@ void ssam_controller_destroy(struct ssam_controller *ctrl)
 	if (ctrl->state == SSAM_CONTROLLER_UNINITIALIZED)
 		return;

-	WARN_ON(ctrl->state != SSAM_CONTROLLER_STOPPED);
+	WARN_ON(ctrl->state != SSAM_CONTROLLER_STOPPED &&
+		ctrl->state != SSAM_CONTROLLER_INITIALIZED);

 	/*
 	 * Note: New events could still have been received after the previous
-- 
2.46.0