linux-kernel - Re: [PATCH 2/3] hwmon: (cros_ec) Add reading target fan RPM function

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Message-ID: <Z9ecN4ZWx1P5csrK@google.com>
Date: Mon, 17 Mar 2025 11:51:19 +0800
From: "Sung-Chi, Li" <lschyi@...omium.org>
To: Thomas Weißschuh <thomas@...ssschuh.net>
Cc: Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>,
	chrome-platform@...ts.linux.dev, linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hwmon: (cros_ec) Add reading target fan RPM function

On Thu, Mar 13, 2025 at 05:24:28PM +0100, Thomas Weißschuh wrote:
> On 2025-03-13 12:47:43+0800, Sung-Chi Li wrote:
> > Implement the functionality of reading the target fan RPM setting from
> > ChromeOS embedded controller under framework.
> > 
> > Signed-off-by: Sung-Chi Li <lschyi@...omium.org>
> > ---
> >  drivers/hwmon/cros_ec_hwmon.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
> > index b2fec0768301f116f49c57b8dbfb042b98a573e1..73bfcbbaf9531be6b753cfef8045fd5dab5b2ab3 100644
> > --- a/drivers/hwmon/cros_ec_hwmon.c
> > +++ b/drivers/hwmon/cros_ec_hwmon.c
> > @@ -36,6 +36,19 @@ static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index
> >  	return 0;
> >  }
> >  
> > +static int cros_ec_hwmon_read_fan_target(struct cros_ec_device *cros_ec, u8 index, int32_t *speed)
> 
> int32_t is a userspace type. In the kernel use i32, or even better u32.
> 
Sorry for missing this important detail, I will not use userspace type
for following changes.

> > +{
> > +	int ret;
> > +	struct ec_response_pwm_get_fan_rpm r;
> 
> Switch the variable declarations around.
> Also call the request "req".
> 
> > +
> > +	ret = cros_ec_cmd(cros_ec, 0, EC_CMD_PWM_GET_FAN_TARGET_RPM, NULL, 0, &r, sizeof(r));
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*speed = le32_to_cpu(r.rpm);
> 
> r.rpm is not marked as __le32, I'm not sure if sparse will complain
> about the usage of le32_to_cpu().
> 
It did. Currently, all devices are running little endians on both AP and EC, so
I think it is ok not to explicitly call the le32_to_cpu?

> > +	return 0;
> > +}
> > +
> >  static int cros_ec_hwmon_read_temp(struct cros_ec_device *cros_ec, u8 index, u8 *temp)
> >  {
> >  	unsigned int offset;
> > @@ -95,6 +108,7 @@ static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> >  {
> >  	struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
> >  	int ret = -EOPNOTSUPP;
> > +	int32_t target_rpm;
> 
> Also u32.
> 
Same for the kernel type changes.

> >  	u16 speed;
> >  	u8 temp;
> >  
> > @@ -111,6 +125,10 @@ static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> >  			ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
> >  			if (ret == 0)
> >  				*val = cros_ec_hwmon_is_error_fan(speed);
> > +		} else if (attr == hwmon_fan_target) {
> > +			ret = cros_ec_hwmon_read_fan_target(priv->cros_ec, channel, &target_rpm);
> > +			if (ret == 0)
> > +				*val = target_rpm;
> >  		}
> >  	} else if (type == hwmon_temp) {
> >  		if (attr == hwmon_temp_input) {
> > 
> > -- 
> > 2.49.0.rc0.332.g42c0ae87b1-goog
> >