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

commit 34eee70a7b82b09dbda4cb453e0e21d460dae226 upstream.

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>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index b8819de1cd8a9407d87088f7ff66a39cbc1d331d..1ce569a405b2637e557c9f31abc89bb3e4cd77f0 100644 (file)
--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -626,6 +626,7 @@ static void ad5933_work(struct work_struct *work)
        struct iio_buffer *ring = indio_dev->buffer;
        signed short buf[2];
        unsigned char status;
+       int ret;
 
        mutex_lock(&indio_dev->mlock);
        if (st->state == AD5933_CTRL_INIT_START_FREQ) {
@@ -633,17 +634,20 @@ 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) {
-               ad5933_i2c_read(st->client,
+               ret = ad5933_i2c_read(st->client,
                                test_bit(1, ring->scan_mask) ?
                                AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
                                ring->scan_count * 2, (u8 *)buf);
+               if (ret)
+                       goto out;
 
                if (ring->scan_count == 2) {
                        buf[0] = be16_to_cpu(buf[0]);
@@ -656,8 +660,7 @@ 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) {
@@ -669,7 +672,7 @@ 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);
 }