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

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Date:   Tue, 16 Apr 2019 15:43:48 +0000
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-hwmon@...r.kernel.org, linux@...ck-us.net, jdelvare@...e.com,
        andrew@...id.au, mine260309@...il.com,
        Eddie James <eajames@...ux.ibm.com>
Subject: [PATCH 1/3] hwmon (occ): Store error condition for rate-limited polls

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>
---
 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 */
 
-- 
2.7.4