linux-kernel - Re: [PATCH v3 0/8] ACPI: thermal: Use trip point table to register thermal zones

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Date:   Tue, 1 Aug 2023 20:39:36 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Michal Wilczynski <michal.wilczynski@...el.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v3 0/8] ACPI: thermal: Use trip point table to register
 thermal zones

On Tue, Aug 1, 2023 at 8:27 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>
>
> Hi Rafael,
>
> On 25/07/2023 14:02, Rafael J. Wysocki wrote:
> > Hi Everyone,
> >
> > This is the second iteration of the $subject patch series and its original
> > description below is still applicable
> >
> > On Tuesday, July 18, 2023 8:01:20 PM CEST Rafael J. Wysocki wrote:
> >>
> >> This patch series makes the ACPI thermal driver register thermal zones
> >> with the help of thermal_zone_device_register_with_trips(), so it
> >> doesn't need to use the thermal zone callbacks related to trip points
> >> any more (and they are dropped in the last patch).
> >>
> >> The approach presented here is quite radically different from the
> >> previous attempts, as it doesn't really rearrange the driver's
> >> internal data structures, but adds the trip table support on top of
> >> them.  For this purpose, it uses an additional field in struct thermal_trip
> >> introduced in the first patch.
> >
> > This update is mostly related to the observation that the critical and hot trip
> > points never change after initialization, so they don't really need to be
> > connected back to the corresponding thermal_trip structures.  It also fixes
> > an error code path memory leak in patch [5/8].
>
> I've been through the series. It is really cool that we can get rid of
> the ops usage at the end of the series.
>
> However, the series introduces a wrapper to the thermal zone lock and
> exports that in the public header. That goes in the opposite direction
> of the recent cleanups and obviously will give the opportunity to
> drivers to do silly things [again].

Because it is necessary to update the trip points in the table under
the zone lock, the driver needs to somehow make that happen.

I suppose I can pass a callback to thermal_zone_device_update() or
similar, but I'm not sure if that's better.

> On the other side, the structure thermal_trip introduces a circular
> reference, which is usually something to avoid.

What do you mean by "a circular reference"?

> Apart those two points, the ACPI changes look ok.
>
> Comments in the different patches will follow

Thanks!