iio: adc: ad7791: 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, 14 insertions, 22 deletions

diff --git a/drivers/iio/adc/ad7791.c b/drivers/iio/adc/ad7791.c
index cf172d58cd44..1dfe6410c64c 100644
--- a/drivers/iio/adc/ad7791.c
+++ b/drivers/iio/adc/ad7791.c
@@ -272,30 +272,22 @@ static ssize_t ad7791_write_frequency(struct device *dev,
         struct ad7791_state *st = iio_priv(indio_dev);
         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 = -EINVAL;
-
-        for (i = 0; i < ARRAY_SIZE(ad7791_sample_freq_avail); i++) {
-                if (sysfs_streq(ad7791_sample_freq_avail[i], buf)) {
-
-                        mutex_lock(&indio_dev->mlock);
-                        st->filter &= ~AD7791_FILTER_RATE_MASK;
-                        st->filter |= i;
-                        ad_sd_write_reg(&st->sd, AD7791_REG_FILTER,
-                                         sizeof(st->filter), st->filter);
-                        mutex_unlock(&indio_dev->mlock);
-                        ret = 0;
+        for (i = 0; i < ARRAY_SIZE(ad7791_sample_freq_avail); i++)
+                if (sysfs_streq(ad7791_sample_freq_avail[i], buf))
                         break;
-                }
-        }
+        if (i == ARRAY_SIZE(ad7791_sample_freq_avail))
+                return -EINVAL;
+
+        ret = iio_device_claim_direct_mode(indio_dev);
+        if (ret)
+                return ret;
+        st->filter &= ~AD7791_FILTER_RATE_MASK;
+        st->filter |= i;
+        ad_sd_write_reg(&st->sd, AD7791_REG_FILTER, sizeof(st->filter),
+                        st->filter);
+        iio_device_release_direct_mode(indio_dev);
 
-        return ret ? ret : len;
+        return len;
 }
 
 static IIO_DEV_ATTR_SAMP_FREQ(S_IWUSR | S_IRUGO,