linux-kernel - Re: [PATCH 3/5] hwmon: (gpio-fan) Ensure lock is held during set_fan

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Message-ID: <98226c50-6f36-40f5-97b8-3ade0dd9ff3c@roeck-us.net>
Date: Sun, 2 Mar 2025 08:54:25 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Alexander Stein <alexander.stein@...tq-group.com>
Cc: Jean Delvare <jdelvare@...e.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-hwmon@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] hwmon: (gpio-fan) Ensure lock is held during
 set_fan_speed()

On Mon, Feb 10, 2025 at 03:59:31PM +0100, Alexander Stein wrote:
> Instead of just documenting by comment, ensure locking per code.
> 
> Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
> ---
>  drivers/hwmon/gpio-fan.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
> index b779240328d59..322b161d5ca1f 100644
> --- a/drivers/hwmon/gpio-fan.c
> +++ b/drivers/hwmon/gpio-fan.c
> @@ -124,9 +124,10 @@ static int __get_fan_ctrl(struct gpio_fan_data *fan_data)
>  	return ctrl_val;
>  }
>  
> -/* Must be called with fan_data->lock held, except during initialization. */
>  static void set_fan_speed(struct gpio_fan_data *fan_data, int speed_index)
>  {
> +	WARN_ON_ONCE(!mutex_is_locked(&fan_data->lock));
> +

No, this just increases code size for no good reason. The comment is
perfectly fine and sufficient.

Guenter