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SubjectRe: [PATCH V2 7/9] hwmon: pwm-fan: add sysfs node to read rpm of fan
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On 03/20/2018 09:40 PM, Rajkumar Rampelli wrote:
> Add fan device attribute fan1_input in pwm-fan driver
> to read speed of fan in rotations per minute.
>
> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
> ---
>
> V2: Removed generic-pwm-tachometer driver and using pwm-fan driver as per suggestions
> to read fan speed.
> Added fan device attribute to report speed of fan in rpms through hwmon sysfs.
>
> drivers/hwmon/pwm-fan.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 70cc0d1..8dda209 100644
> --- a/drivers/hwmon/pwm-fan.c
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -98,11 +98,34 @@ static ssize_t show_pwm(struct device *dev,
> return sprintf(buf, "%u\n", ctx->pwm_value);
> }
>
> +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + struct pwm_fan_ctx *ptt = dev_get_drvdata(dev);
> + struct pwm_device *pwm = ptt->pwm;
> + struct pwm_capture result;
> + unsigned int rpm = 0;
> + int ret;
> +
> + ret = pwm_capture(pwm, &result, 0);
> + if (ret < 0) {
> + pr_err("Failed to capture PWM: %d\n", ret);
> + return ret;
> + }
> +
> + if (result.period)
> + rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
> + result.period);
> +
> + return sprintf(buf, "%u\n", rpm);
> +}
>
> static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, show_pwm, set_pwm, 0);
> +static SENSOR_DEVICE_ATTR(fan1_input, 0444, show_rpm, NULL, 0);
>
> static struct attribute *pwm_fan_attrs[] = {
> &sensor_dev_attr_pwm1.dev_attr.attr,
> + &sensor_dev_attr_fan1_input.dev_attr.attr,

This doesn't make sense. The same pwm can not both control the fan speed
and report it.

Guenter

> NULL,
> };
>
>

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