[PATCH] hwmon: (emc2103) fix unable to change fan pwm1_enable attribute

[PATCH] hwmon: (emc2103) fix unable to change fan pwm1_enable attribute

[Vishwas M]

This patch fixes a bug which does not let FAN mode to be changed from
sysfs(pwm1_enable). i.e pwm1_enable can not be set to 3, it will always
remain at 0.

This is caused because the device driver handles the result of
"read_u8_from_i2c(client, REG_FAN_CONF1, &conf_reg)" incorrectly. The
driver thinks an error has occurred if the (result != 0). This has been
fixed by changing the condition to (result < 0).

Signed-off-by: Vishwas M <vishwas.reddy.vr@gmail.com>
---
 drivers/hwmon/emc2103.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
index 491a570e8e50..924c02c1631d 100644
--- a/drivers/hwmon/emc2103.c
+++ b/drivers/hwmon/emc2103.c
@@ -443,7 +443,7 @@ static ssize_t pwm1_enable_store(struct device *dev,
 	}
 
 	result = read_u8_from_i2c(client, REG_FAN_CONF1, &conf_reg);
-	if (result) {
+	if (result < 0) {
 		count = result;
 		goto err;
 	}
-- 
2.25.1

Re: [PATCH] hwmon: (emc2103) fix unable to change fan pwm1_enable attribute

[Guenter Roeck]

On 7/7/20 7:27 AM, Vishwas M wrote:
> This patch fixes a bug which does not let FAN mode to be changed from
> sysfs(pwm1_enable). i.e pwm1_enable can not be set to 3, it will always
> remain at 0.
> 
> This is caused because the device driver handles the result of
> "read_u8_from_i2c(client, REG_FAN_CONF1, &conf_reg)" incorrectly. The
> driver thinks an error has occurred if the (result != 0). This has been
> fixed by changing the condition to (result < 0).
> 
> Signed-off-by: Vishwas M <vishwas.reddy.vr@gmail.com>
> ---
>  drivers/hwmon/emc2103.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
> index 491a570e8e50..924c02c1631d 100644
> --- a/drivers/hwmon/emc2103.c
> +++ b/drivers/hwmon/emc2103.c
> @@ -443,7 +443,7 @@ static ssize_t pwm1_enable_store(struct device *dev,
>  	}
>  
>  	result = read_u8_from_i2c(client, REG_FAN_CONF1, &conf_reg);
> -	if (result) {
> +	if (result < 0) {
>  		count = result;
>  		goto err;
>  	}
> 

The underlying problem is really that read_u8_from_i2c()
returns the value twice - once as return code, and once
written into the passed pointer. This unnecessarily complex
and messy. But, still, valid bug and fix. Applied.

Thanks,
Guenter