iio: buffer: Return error if no callback is given

mainline inclusion
from mainline-v5.11-rc1
commit 6d74a3ee
category: bugfix
bugzilla: 185695 https://gitee.com/openeuler/kernel/issues/I4DDEL

Return error in case no callback is provided to
`iio_channel_get_all_cb()`. There's no point in setting up a buffer-cb
if no callback is provided.
Signed-off-by: NNuno Sá <nuno.sa@analog.com>
Reviewed-by: NOlivier Moysan <olivier.moysan@st.com>
Link: https://lore.kernel.org/r/20201121161457.957-3-nuno.sa@analog.comSigned-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Ntanghui <tanghui20@huawei.com>
Reviewed-by: NZhang Qiao <zhangqiao22@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/iio/buffer/industrialio-buffer-cb.c

@@ -54,6 +54,11 @@ struct iio_cb_buffer *iio_channel_get_all_cb(struct device *dev,
 	struct iio_cb_buffer *cb_buff;
 	struct iio_channel *chan;
 
+	if (!cb) {
+		dev_err(dev, "Invalid arguments: A callback must be provided!\n");
+		return ERR_PTR(-EINVAL);
+	}
+
 	cb_buff = kzalloc(sizeof(*cb_buff), GFP_KERNEL);
 	if (cb_buff == NULL)
 		return ERR_PTR(-ENOMEM);