linux-kernel - Re: [PATCH 1/3] hwmon (occ): Store error condition for rate-limited polls

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Message-ID: <20190416221231.GA31987@roeck-us.net>
Date:   Tue, 16 Apr 2019 15:12:31 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        jdelvare@...e.com, andrew@...id.au, mine260309@...il.com
Subject: Re: [PATCH 1/3] hwmon (occ): Store error condition for rate-limited
 polls

On Tue, Apr 16, 2019 at 03:43:48PM +0000, 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@...ux.ibm.com>

Applied.

Thanks,
Guenter

> ---
>  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 9d197e9..13a6290 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -141,6 +141,7 @@ 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;
>  
> @@ -149,6 +150,7 @@ 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 */
> @@ -210,6 +212,8 @@ 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 ed2cf42..fc13f3c 100644
> --- a/drivers/hwmon/occ/common.h
> +++ b/drivers/hwmon/occ/common.h
> @@ -106,7 +106,8 @@ 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 */
>