iio: buffer: Make length attribute read only for buffers without set_length
If a buffer implementation does not implement the set_length() callback the
length will be static and can not be changed by userspace. Mark the length
attribute as a read only property in this case so userspace is aware of this
rather than just silently accepting any length value.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index ba89357..4ca4c0a 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -418,8 +418,7 @@
if (iio_buffer_is_active(indio_dev->buffer)) {
ret = -EBUSY;
} else {
- if (buffer->access->set_length)
- buffer->access->set_length(buffer, val);
+ buffer->access->set_length(buffer, val);
ret = 0;
}
mutex_unlock(&indio_dev->mlock);
@@ -760,6 +759,8 @@
static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
iio_buffer_write_length);
+static struct device_attribute dev_attr_length_ro = __ATTR(length,
+ S_IRUGO, iio_buffer_read_length, NULL);
static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
iio_buffer_show_enable, iio_buffer_store_enable);
@@ -786,7 +787,10 @@
if (!buffer->buffer_group.attrs)
return -ENOMEM;
- buffer->buffer_group.attrs[0] = &dev_attr_length.attr;
+ if (buffer->access->set_length)
+ buffer->buffer_group.attrs[0] = &dev_attr_length.attr;
+ else
+ buffer->buffer_group.attrs[0] = &dev_attr_length_ro.attr;
buffer->buffer_group.attrs[1] = &dev_attr_enable.attr;
if (buffer->attrs)
memcpy(&buffer->buffer_group.attrs[2], buffer->attrs,