linux-kernel - Re: [PATCH 6.6] thermal/of: Fix mask mismatch when no trips subnode

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Message-ID: <2025071012-granola-daylong-9943@gregkh>
Date: Thu, 10 Jul 2025 15:33:17 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Hsin-Te Yuan <yuanhsinte@...omium.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Amit Kucheria <amitk@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 6.6] thermal/of: Fix mask mismatch when no trips subnode

On Mon, Jul 07, 2025 at 06:27:10PM +0800, Hsin-Te Yuan wrote:
> After commit 725f31f300e3 ("thermal/of: support thermal zones w/o trips
> subnode") was backported on 6.6 stable branch as commit d3304dbc2d5f
> ("thermal/of: support thermal zones w/o trips subnode"), thermal zones
> w/o trips subnode still fail to register since `mask` argument is not
> set correctly. When number of trips subnode is 0, `mask` must be 0 to
> pass the check in `thermal_zone_device_register_with_trips()`.
> 
> Set `mask` to 0 when there's no trips subnode.
> 
> Signed-off-by: Hsin-Te Yuan <yuanhsinte@...omium.org>
> ---
>  drivers/thermal/thermal_of.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index 0f520cf923a1e684411a3077ad283551395eec11..97aeb869abf5179dfa512dd744725121ec7fd0d9 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -514,7 +514,7 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
>  	of_ops->bind = thermal_of_bind;
>  	of_ops->unbind = thermal_of_unbind;
>  
> -	mask = GENMASK_ULL((ntrips) - 1, 0);
> +	mask = ntrips ? GENMASK_ULL((ntrips) - 1, 0) : 0;

Meta-comment, I hate ? : lines in C, especially when they are not
needed, like here.  Spell this out, with a real if statement please, so
that we can read and easily understand what is going on.

That being said, I agree with Rafael, let's do whatever is in mainline
instead.  Fix it the same way it was fixed there by backporting the
relevant commits.

thanks,

greg k-h