[PATCH v2 3/7] iio: adc: ad7793: claim direct mode when writing frequency

Alison Schofield
2016-06-02T04:28:19Z

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>
---
Changes in v2
Refactored function per reviewers comments
Updated changelog

drivers/iio/adc/ad7793.c | 32 +++++++++++++-------------------
1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
index 7b07bb6..a43722f 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,
--
2.1.4