On 05/26/2017 07:48 AM, Patrick Venture wrote:
When the controller fails to provide an RPM reading within the allotted time; the driver returns -EAGAIN instead of 0. Signed-off-by: Patrick Venture <venture@xxxxxxxxxx <mailto:venture@xxxxxxxxxx>> --- drivers/hwmon/aspeed-pwm-tacho.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c index 48403a2115be..ec57be4a4a55 100644 --- a/drivers/hwmon/aspeed-pwm-tacho.c +++ b/drivers/hwmon/aspeed-pwm-tacho.c @@ -7,6 +7,7 @@ */ #include <linux/clk.h> +#include <linux/errno.h> #include <linux/gpio/consumer.h> #include <linux/delay.h> #include <linux/hwmon.h> @@ -516,7 +517,7 @@ static u32 aspeed_get_fan_tach_ch_rpm(struct aspeed_pwm_tacho_data *priv, clk_source = priv->clk_freq; if (raw_data == 0) -return 0; +return -EAGAIN;
We don't know why the value reported is 0. Maybe it is because no fan is connected. We can not just return -EAGAIN; this might result in a tight loop if the problem is permanent. A retry loop which returns -ETIMEOUT after some reasonable timeout might be more appropriate if the controller just needs more time, and if reading "0" is an indication that the controller is not ready. Note that you can not just return an error without changing the function type to int.
return (clk_source * 60) / (2 * raw_data * tach_div); } @@ -566,7 +567,7 @@ static ssize_t show_rpm(struct device *dev, struct device_attribute *attr, rpm = aspeed_get_fan_tach_ch_rpm(priv, index); -return sprintf(buf, "%u\n", rpm); +return sprintf(buf, "%d\n", rpm);
rpm is u32. This is incorrect. This would also return a negative speed to the user, not an error. To return an error, the variable would have to be an int, and the code would have to be something like int rpm; ... rpm = aspeed_get_fan_tach_ch_rpm(priv, index); if (rpm < 0) return rpm; return sprintf(...); Guenter
} static umode_t pwm_is_visible(struct kobject *kobj, -- 2.13.0.219.gdb65acc882-goog
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