staging: iio: ad5933: avoid uninitialized variable in error case

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>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index 5eecf1c..3892a74 100644 (file)
--- 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);
 }