Re: [PATCH dev-5.0 1/2] hwmon (occ): Store error condition for rate-limited polls

[Andrew Jeffery]

On Tue, 16 Apr 2019, at 07:59, Eddie James wrote:
> The OCC driver limits the rate of sending poll commands to the OCC. If a
> user reads a hwmon entry after a poll response resulted in an error and
> is rate-limited, the error is invisible to the user. Fix this by storing
> the last error and returning that in the rate-limited case.
> 
> Signed-off-by: Eddie James <eajames at linux.ibm.com>

Should this be sent upstream?

> ---
>  drivers/hwmon/occ/common.c | 4 ++++
>  drivers/hwmon/occ/common.h | 3 ++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index c888f4a..0e812ef 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -138,6 +138,7 @@ static int occ_poll(struct occ *occ)
>  	/* mutex should already be locked if necessary */
>  	rc = occ->send_cmd(occ, cmd);
>  	if (rc) {
> +		occ->last_error = rc;
>  		if (occ->error_count++ > OCC_ERROR_COUNT_THRESHOLD)
>  			occ->error = rc;
>  
> @@ -146,6 +147,7 @@ static int occ_poll(struct occ *occ)
>  
>  	/* clear error since communication was successful */
>  	occ->error_count = 0;
> +	occ->last_error = 0;
>  	occ->error = 0;
>  
>  	/* check for safe state */
> @@ -207,6 +209,8 @@ int occ_update_response(struct occ *occ)
>  	if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
>  		rc = occ_poll(occ);
>  		occ->last_update = jiffies;
> +	} else {
> +		rc = occ->last_error;
>  	}
>  
>  	mutex_unlock(&occ->lock);
> diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
> index 7c44df3..c676e48 100644
> --- a/drivers/hwmon/occ/common.h
> +++ b/drivers/hwmon/occ/common.h
> @@ -105,7 +105,8 @@ struct occ {
>  	struct attribute_group group;
>  	const struct attribute_group *groups[2];
>  
> -	int error;                      /* latest transfer error */
> +	int error;                      /* final transfer error after retry */
> +	int last_error;			/* latest transfer error */
>  	unsigned int error_count;       /* number of xfr errors observed */
>  	unsigned long last_safe;        /* time OCC entered "safe" state */
>  
> -- 
> 2.7.4
> 
>