iio: adc: ad7793: claim direct mode when writing frequency

Driver was checking for direct mode and trying to lock it, but
left a gap where mode could change before the desired operation.
Use iio_device_claim_direct_mode() to guarantee device stays in
direct mode.

Refactor function to clarify look-up followed by lock sequence.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Cc: Daniel Baluta <daniel.baluta@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 13 insertions, 19 deletions

diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
index 7b07bb651671..a43722fbf03a 100644
--- a/drivers/iio/adc/ad7793.c
+++ b/drivers/iio/adc/ad7793.c
@@ -369,13 +369,6 @@ static ssize_t ad7793_write_frequency(struct device *dev,
         long lval;
         int i, ret;
 
-        mutex_lock(&indio_dev->mlock);
-        if (iio_buffer_enabled(indio_dev)) {
-                mutex_unlock(&indio_dev->mlock);
-                return -EBUSY;
-        }
-        mutex_unlock(&indio_dev->mlock);
-
         ret = kstrtol(buf, 10, &lval);
         if (ret)
                 return ret;
@@ -383,20 +376,21 @@ static ssize_t ad7793_write_frequency(struct device *dev,
         if (lval == 0)
                 return -EINVAL;
 
-        ret = -EINVAL;
-
         for (i = 0; i < 16; i++)
-                if (lval == st->chip_info->sample_freq_avail[i]) {
-                        mutex_lock(&indio_dev->mlock);
-                        st->mode &= ~AD7793_MODE_RATE(-1);
-                        st->mode |= AD7793_MODE_RATE(i);
-                        ad_sd_write_reg(&st->sd, AD7793_REG_MODE,
-                                         sizeof(st->mode), st->mode);
-                        mutex_unlock(&indio_dev->mlock);
-                        ret = 0;
-                }
+                if (lval == st->chip_info->sample_freq_avail[i])
+                        break;
+        if (i == 16)
+                return -EINVAL;
 
-        return ret ? ret : len;
+        ret = iio_device_claim_direct_mode(indio_dev);
+        if (ret)
+                return ret;
+        st->mode &= ~AD7793_MODE_RATE(-1);
+        st->mode |= AD7793_MODE_RATE(i);
+        ad_sd_write_reg(&st->sd, AD7793_REG_MODE, sizeof(st->mode), st->mode);
+        iio_device_release_direct_mode(indio_dev);
+
+        return len;
 }
 
 static IIO_DEV_ATTR_SAMP_FREQ(S_IWUSR | S_IRUGO,