linux-kernel - Re: [PATCH RESEND] thermal: broadcom: Use clamp to simplify bcm2835_thermal

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Message-ID: <20260105222755.305787f7@pumpkin>
Date: Mon, 5 Jan 2026 22:27:55 +0000
From: David Laight <david.laight.linux@...il.com>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano
 <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, Lukasz Luba
 <lukasz.luba@....com>, Florian Fainelli <florian.fainelli@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Ray Jui <rjui@...adcom.com>, Scott
 Branden <sbranden@...adcom.com>, Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>, linux-pm@...r.kernel.org,
 linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] thermal: broadcom: Use clamp to simplify
 bcm2835_thermal_temp2adc

On Mon,  5 Jan 2026 13:13:03 +0100
Thorsten Blum <thorsten.blum@...ux.dev> wrote:

> Use clamp() to simplify bcm2835_thermal_temp2adc() and improve its
> readability. Explicitly cast BIT() to int to prevent a signedness error.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>  drivers/thermal/broadcom/bcm2835_thermal.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
> index 685a5aee5e0d..c5105dfc6ec9 100644
> --- a/drivers/thermal/broadcom/bcm2835_thermal.c
> +++ b/drivers/thermal/broadcom/bcm2835_thermal.c
> @@ -11,6 +11,7 @@
>  #include <linux/err.h>
>  #include <linux/io.h>
>  #include <linux/kernel.h>
> +#include <linux/minmax.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> @@ -80,12 +81,7 @@ static int bcm2835_thermal_temp2adc(int temp, int offset, int slope)
>  	temp -= offset;
>  	temp /= slope;
>  
> -	if (temp < 0)
> -		temp = 0;
> -	if (temp >= BIT(BCM2835_TS_TSENSSTAT_DATA_BITS))
> -		temp = BIT(BCM2835_TS_TSENSSTAT_DATA_BITS) - 1;
> -
> -	return temp;
> +	return clamp(temp, 0, (int)BIT(BCM2835_TS_TSENSSTAT_DATA_BITS) - 1);

Hmmm....
I wonder if I can get 'statically_true(lo >= 0)' into the type check so that
cast isn't necessary.
	signed_val < 0 ? 0 : signed_val > unsigned_val ? unsigned_val : signed_val
is fine.
Would mean swapping the order of the tests - which shouldn't break anything.
But will need a full audit - various bits of code have relied on the order
of the comparisons.

	David

>  }
>  
>  static int bcm2835_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
>