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misc: hmc6352: fix wrong return value checking for i2c_master_recv

PATCH In review Axel Lin 2 participants 2 messages Mar 9, 2011 Char and misc drivers

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Axel Lin

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PATCH 1/1 misc: hmc6352: fix wrong return value checking for i2c_master_recv

i2c_master_recv() returns negative errno, or else the number of bytes read. Thus i2c_master_recv(client, i2c_data, 2) returns 2 instead of 1 in success case.

Signed-off-by Axel Lin <[email protected]>
---
 drivers/misc/hmc6352.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
drivers/misc/hmc6352.c +1 -1
index 234bfca..3afc11e 100644
@@ -86,7 +86,7 @@ static ssize_t compass_heading_data_show(struct device *dev,
 	msleep(10); /* sending 'A' cmd we need to wait for 7-10 millisecs */
 	ret = i2c_master_recv(client, i2c_data, 2);
 	mutex_unlock(&compass_mutex);
-	if (ret != 1) {
+	if (ret < 0) {
 		dev_warn(dev, "i2c read data cmd failed\n");
 		return ret;
 	}
Signature · 1 line
1.7.2
#1 lore raw
Quoted 13 lines · On Wed, 09 Mar 2011 16:41:56 +0800 Axel Lin <[email protected]> wrote:

i2c_master_recv() returns negative errno, or else the number of bytes read. Thus i2c_master_recv(client, i2c_data, 2) returns 2 instead of 1 in success case.

Signed-off-by Axel Lin <[email protected]>
---
 drivers/misc/hmc6352.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
drivers/misc/hmc6352.c +0 -0
index 234bfca..3afc11e 100644

drivers/misc/hmc6352.c static ssize_t compass_heading_data_show(struct device *dev, · line 92

Quoted 8 lines
drivers/misc/hmc6352.c +1 -1
@@ -86,7 +86,7 @@ static ssize_t compass_heading_data_show(struct device *dev,
 	msleep(10); /* sending 'A' cmd we need to wait for 7-10 millisecs */
 	ret = i2c_master_recv(client, i2c_data, 2);
 	mutex_unlock(&compass_mutex);
-	if (ret != 1) {
+	if (ret < 0) {
 		dev_warn(dev, "i2c read data cmd failed\n");
 		return ret;
 	}

The problem seems real but the fix won't work:

drivers/misc/hmc6352.c renamed from drivers/misc/hmc6352.c~drivers-misc-hmc6352c-fix-wrong-return-value-checking-for-i2c_master_recv-fix +1 -1
@@ -75,7 +75,7 @@ static ssize_t compass_heading_data_show
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	unsigned char i2c_data[2];
-	unsigned int ret;
+	int ret;
 
 	mutex_lock(&compass_mutex);
 	ret = compass_command(client, 'A');

I also wonder if this bit is correct:

: static ssize_t compass_heading_data_show(struct device *dev,
: struct device_attribute *attr, char *buf)
: {
: struct i2c_client *client = to_i2c_client(dev);
: unsigned char i2c_data[2];
: int ret;
:
: mutex_lock(&compass_mutex);
: ret = compass_command(client, 'A');
: if (ret != 1) {
: mutex_unlock(&compass_mutex);
: return ret;
: }

If compass_command() returns zero (short write on i2c?!?!?) then did we do the right thing?