linux-kernel - Re: [PATCH] thermal/sysfs: Always enable hysteresis write support

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Date: Tue, 9 Jan 2024 14:42:52 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Manaf Meethalavalappu Pallikunhi <quic_manafm@...cinc.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal/sysfs: Always enable hysteresis write support

On Sat, Jan 6, 2024 at 8:16 PM Manaf Meethalavalappu Pallikunhi
<quic_manafm@...cinc.com> wrote:
>
> The commit 2e38a2a981b2("thermal/core: Add a generic
> thermal_zone_set_trip() function") adds the support to update
> trip hysteresis even if set_trip_hyst() operation is not defined.
> But during hysteresis attribute creation, if this operation is
> defined then only it enables hysteresis write access. It leads
> to a case where hysteresis sysfs will be read only for a thermal
> zone when its set_trip_hyst() operation is not defined.

Which is by design.

For some thermal zone types (eg. acpi), updating trip hysteresis via
sysfs might lead to incorrect behavior.