linux-kernel - Re: [PATCH v2 4/6] thermal: core: Store zone ops in struct thermal_zone

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Date: Thu, 22 Feb 2024 11:47:34 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Linux ACPI <linux-acpi@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Zhang Rui <rui.zhang@...el.com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>, NXP Linux Team <linux-imx@....com>
Subject: Re: [PATCH v2 4/6] thermal: core: Store zone ops in struct
 thermal_zone_device

On 14/02/2024 13:45, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The current code requires thermal zone creators to pass pointers to
> writable ops structures to thermal_zone_device_register_with_trips()
> which needs to modify the target struct thermal_zone_device_ops object
> if the "critical" operation in it is NULL.
> 
> Moreover, the callers of thermal_zone_device_register_with_trips() are
> required to hold on to the struct thermal_zone_device_ops object passed
> to it until the given thermal zone is unregistered.
> 
> Both of these requirements are quite inconvenient, so modify struct
> thermal_zone_device to contain struct thermal_zone_device_ops as field and
> make thermal_zone_device_register_with_trips() copy the contents of the
> struct thermal_zone_device_ops passed to it via a pointer (which can be
> const now) to that field.
> 
> Also adjust the code using thermal zone ops accordingly and modify
> thermal_of_zone_register() to use a local ops variable during
> thermal zone registration so ops do not need to be freed in
> thermal_of_zone_unregister() any more.

[ ... ]

>   static void thermal_of_zone_unregister(struct thermal_zone_device *tz)
>   {
>   	struct thermal_trip *trips = tz->trips;
> -	struct thermal_zone_device_ops *ops = tz->ops;
>   
>   	thermal_zone_device_disable(tz);
>   	thermal_zone_device_unregister(tz);
>   	kfree(trips);

Not related to the current patch but with patch 1/6. Freeing the trip 
points here will lead to a double free given it is already freed from 
thermal_zone_device_unregister() after the changes introduces in patch 
1, right ?

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