iio: Specify supported modes for buffers

For each buffer type specify the supported device modes for this buffer.
This allows us for devices which support multiple different operating modes
to pick the correct operating mode based on the modes supported by the
attached buffers.

It also prevents that buffers with conflicting modes are attached
to a device at the same time or that a buffer with a non-supported mode is
attached to a device (e.g. in-kernel callback buffer to a device only
supporting hardware mode).

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 19 insertions, 3 deletions

diff --git a/drivers/iio/buffer_cb.c b/drivers/iio/buffer_cb.c
index eb46e728aa2e..1648e6e5a848 100644
--- a/drivers/iio/buffer_cb.c
+++ b/drivers/iio/buffer_cb.c
@@ -33,6 +33,8 @@ static void iio_buffer_cb_release(struct iio_buffer *buffer)
 static const struct iio_buffer_access_funcs iio_cb_access = {
 	.store_to = &iio_buffer_cb_store_to,
 	.release = &iio_buffer_cb_release,
+
+	.modes = INDIO_BUFFER_SOFTWARE | INDIO_BUFFER_TRIGGERED,
 };
 
 struct iio_cb_buffer *iio_channel_get_all_cb(struct device *dev,
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 209c7ad793c5..0a14bd825fe0 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -604,6 +604,7 @@ static int iio_verify_update(struct iio_dev *indio_dev,
 	const unsigned long *scan_mask;
 	struct iio_buffer *buffer;
 	bool scan_timestamp;
+	unsigned int modes;
 
 	memset(config, 0, sizeof(*config));
 
@@ -615,12 +616,23 @@ static int iio_verify_update(struct iio_dev *indio_dev,
 		list_is_singular(&indio_dev->buffer_list))
 			return 0;
 
+	modes = indio_dev->modes;
+
+	list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
+		if (buffer == remove_buffer)
+			continue;
+		modes &= buffer->access->modes;
+	}
+
+	if (insert_buffer)
+		modes &= insert_buffer->access->modes;
+
 	/* Definitely possible for devices to support both of these. */
-	if ((indio_dev->modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
+	if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
 		config->mode = INDIO_BUFFER_TRIGGERED;
-	} else if (indio_dev->modes & INDIO_BUFFER_HARDWARE) {
+	} else if (modes & INDIO_BUFFER_HARDWARE) {
 		config->mode = INDIO_BUFFER_HARDWARE;
-	} else if (indio_dev->modes & INDIO_BUFFER_SOFTWARE) {
+	} else if (modes & INDIO_BUFFER_SOFTWARE) {
 		config->mode = INDIO_BUFFER_SOFTWARE;
 	} else {
 		/* Can only occur on first buffer */
diff --git a/drivers/iio/kfifo_buf.c b/drivers/iio/kfifo_buf.c
index 847ca561afe0..db15684a4731 100644
--- a/drivers/iio/kfifo_buf.c
+++ b/drivers/iio/kfifo_buf.c
@@ -135,6 +135,8 @@ static const struct iio_buffer_access_funcs kfifo_access_funcs = {
 	.set_bytes_per_datum = &iio_set_bytes_per_datum_kfifo,
 	.set_length = &iio_set_length_kfifo,
 	.release = &iio_kfifo_buffer_release,
+
+	.modes = INDIO_BUFFER_SOFTWARE | INDIO_BUFFER_TRIGGERED,
 };
 
 struct iio_buffer *iio_kfifo_allocate(void)