linux-kernel - [PATCH v1 1/4] rtc: pcf2127: fix reading uninitialized value on RTC_READ

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Message-Id: <1443777442-15920-2-git-send-email-u.kleine-koenig@pengutronix.de>
Date:	Fri,  2 Oct 2015 11:17:19 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, kernel@...gutronix.de,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/4] rtc: pcf2127: fix reading uninitialized value on RTC_READ_VL ioctl

The flag reported on the RTC_READ_VL ioctl is only initialized when the
date is read out. So the voltage low value doesn't represent reality but
the status at the time the date was read (or 0 if the date was not read
yet).

Moreover when userspace requests a value via an ioctl there is no added
benefit to also make a prosa representation of this (and other) values
appear in the kernel log so remove the calls to dev_info and the driver
data members to track their state.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---

Notes:
    While this is a fix I don't think it is critical enough to backport it to
    stable (or apply it during the rc phase).
    
    Looking at
    
    	http://codesearch.debian.net/perpackage-results/RTC_VL_READ
    
    this ioctl isn't used much.

 drivers/rtc/rtc-pcf2127.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
index 4c7738f706c1..4f66c4216b5a 100644
--- a/drivers/rtc/rtc-pcf2127.c
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -39,8 +39,6 @@ static struct i2c_driver pcf2127_driver;
 
 struct pcf2127 {
 	struct rtc_device *rtc;
-	int voltage_low; /* indicates if a low_voltage was detected */
-	int oscillator_failed; /* OSF was detected and date is unreliable */
 };
 
 /*
@@ -49,7 +47,6 @@ struct pcf2127 {
  */
 static int pcf2127_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
-	struct pcf2127 *pcf2127 = i2c_get_clientdata(client);
 	unsigned char buf[10] = { PCF2127_REG_CTRL1 };
 
 	/* read registers */
@@ -59,18 +56,15 @@ static int pcf2127_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 		return -EIO;
 	}
 
-	if (buf[PCF2127_REG_CTRL3] & 0x04) {
-		pcf2127->voltage_low = 1;
+	if (buf[PCF2127_REG_CTRL3] & 0x04)
 		dev_info(&client->dev,
 			"low voltage detected, check/replace RTC battery.\n");
-	}
 
 	if (buf[PCF2127_REG_SC] & PCF2127_OSF) {
 		/*
 		 * no need clear the flag here,
 		 * it will be cleared once the new date is saved
 		 */
-		pcf2127->oscillator_failed = 1;
 		dev_warn(&client->dev,
 			 "oscillator stop detected, date/time is not reliable\n");
 		return -EINVAL;
@@ -107,7 +101,6 @@ static int pcf2127_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 
 static int pcf2127_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
-	struct pcf2127 *pcf2127 = i2c_get_clientdata(client);
 	unsigned char buf[8];
 	int i = 0, err;
 
@@ -141,9 +134,6 @@ static int pcf2127_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 		return -EIO;
 	}
 
-	/* clear OSF flag in client data */
-	pcf2127->oscillator_failed = 0;
-
 	return 0;
 }
 
@@ -151,17 +141,27 @@ static int pcf2127_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 static int pcf2127_rtc_ioctl(struct device *dev,
 				unsigned int cmd, unsigned long arg)
 {
-	struct pcf2127 *pcf2127 = i2c_get_clientdata(to_i2c_client(dev));
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char buf = PCF2127_REG_CTRL3;
+	int ret;
 
 	switch (cmd) {
 	case RTC_VL_READ:
-		if (pcf2127->voltage_low)
-			dev_info(dev, "low voltage detected, check/replace battery\n");
-		if (pcf2127->oscillator_failed)
-			dev_info(dev, "oscillator stop detected, date/time is not reliable\n");
+		ret = i2c_master_send(client, &buf, 1);
+		if (!ret)
+			ret = -EIO;
+		if (ret < 0)
+			return ret;
+
+		ret = i2c_master_recv(client, &buf, 1);
+		if (!ret)
+			ret = -EIO;
+		if (ret < 0)
+			return ret;
+
+		buf = buf & PCF2127_REG_CTRL3_BLF ? 1 : 0;
 
-		if (copy_to_user((void __user *)arg, &pcf2127->voltage_low,
-					sizeof(int)))
+		if (copy_to_user((void __user *)arg, &buf, sizeof(int)))
 			return -EFAULT;
 		return 0;
 	default:
-- 
2.6.0

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