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Subject[PATCH] [v2] staging: iio: ad5933: avoid uninitialized variable in error case
Date
The ad5933_i2c_read function returns an error code to indicate
whether it could read data or not. However ad5933_work() ignores
this return code and just accesses the data unconditionally,
which gets detected by gcc as a possible bug:

drivers/staging/iio/impedance-analyzer/ad5933.c: In function 'ad5933_work':
drivers/staging/iio/impedance-analyzer/ad5933.c:649:16: warning: 'status' may be used uninitialized in this function [-Wmaybe-uninitialized]

This adds minimal error handling so we only evaluate the
data if it was correctly read.

Link: https://patchwork.kernel.org/patch/8110281/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: handle failure for both affected reads instead of just the one
we get a warning for
v2: do not retry on failure to avoid looping in case of permanent
errors
---
drivers/staging/iio/impedance-analyzer/ad5933.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index 5eecf1cb1028..3892a7470410 100644
--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -655,6 +655,7 @@ static void ad5933_work(struct work_struct *work)
__be16 buf[2];
int val[2];
unsigned char status;
+ int ret;

mutex_lock(&indio_dev->mlock);
if (st->state == AD5933_CTRL_INIT_START_FREQ) {
@@ -662,19 +663,22 @@ static void ad5933_work(struct work_struct *work)
ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
st->state = AD5933_CTRL_START_SWEEP;
schedule_delayed_work(&st->work, st->poll_time_jiffies);
- mutex_unlock(&indio_dev->mlock);
- return;
+ goto out;
}

- ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+ ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+ if (ret)
+ goto out;

if (status & AD5933_STAT_DATA_VALID) {
int scan_count = bitmap_weight(indio_dev->active_scan_mask,
indio_dev->masklength);
- ad5933_i2c_read(st->client,
+ ret = ad5933_i2c_read(st->client,
test_bit(1, indio_dev->active_scan_mask) ?
AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
scan_count * 2, (u8 *)buf);
+ if (ret)
+ goto out;

if (scan_count == 2) {
val[0] = be16_to_cpu(buf[0]);
@@ -686,8 +690,7 @@ static void ad5933_work(struct work_struct *work)
} else {
/* no data available - try again later */
schedule_delayed_work(&st->work, st->poll_time_jiffies);
- mutex_unlock(&indio_dev->mlock);
- return;
+ goto out;
}

if (status & AD5933_STAT_SWEEP_DONE) {
@@ -700,7 +703,7 @@ static void ad5933_work(struct work_struct *work)
ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
schedule_delayed_work(&st->work, st->poll_time_jiffies);
}
-
+out:
mutex_unlock(&indio_dev->mlock);
}

--
2.9.0
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