staging:iio: Make write_event_value callback optional

Some devices have fixed thresholds which can not be modified so make the
write_event_value callback optional, so the drivers for these devices do not
have to implement a boilerplate no-op callback.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/iio/industrialio-core.c b/drivers/staging/iio/industrialio-core.c
index dc2339ae63d056cde37796fc9108d8696267eb04..0b671663b55d2b9d1c9d07fc566f530f9edbef13 100644 (file)
--- a/drivers/staging/iio/industrialio-core.c
+++ b/drivers/staging/iio/industrialio-core.c
@@ -790,6 +790,9 @@ static ssize_t iio_ev_value_store(struct device *dev,
        unsigned long val;
        int ret;
 
+       if (!indio_dev->info->write_event_value)
+               return -EINVAL;
+
        ret = strict_strtoul(buf, 10, &val);
        if (ret)
                return ret;