Patch "iio: core: introduce iio_device_{claim|release}_buffer_mode() APIs" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    iio: core: introduce iio_device_{claim|release}_buffer_mode() APIs

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iio-core-introduce-iio_device_-claim-release-_buffer.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fccabee084dbdfcf4c6ae3dfd48ece37e52362ab
Author: Nuno Sá <nuno.sa@xxxxxxxxxx>
Date:   Wed Oct 12 17:16:17 2022 +0200

    iio: core: introduce iio_device_{claim|release}_buffer_mode() APIs
    
    [ Upstream commit 0a8565425afd8ba0e1a0ea73e21da119ee6dacea ]
    
    These APIs are analogous to iio_device_claim_direct_mode() and
    iio_device_release_direct_mode() but, as the name suggests, with the
    logic flipped. While this looks odd enough, it will have at least two
    users (in following changes) and it will be important to move the IIO
    mlock to the private struct.
    
    Signed-off-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
    Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20221012151620.1725215-2-nuno.sa@xxxxxxxxxx
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
    Stable-dep-of: 7771c8c80d62 ("iio: cros_ec: fix an use-after-free in cros_ec_sensors_push_data()")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 6145e6e4f0ffd..78c780d1ab897 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -2084,6 +2084,44 @@ void iio_device_release_direct_mode(struct iio_dev *indio_dev)
 }
 EXPORT_SYMBOL_GPL(iio_device_release_direct_mode);
 
+/**
+ * iio_device_claim_buffer_mode - Keep device in buffer mode
+ * @indio_dev:	the iio_dev associated with the device
+ *
+ * If the device is in buffer mode it is guaranteed to stay
+ * that way until iio_device_release_buffer_mode() is called.
+ *
+ * Use with iio_device_release_buffer_mode().
+ *
+ * Returns: 0 on success, -EBUSY on failure.
+ */
+int iio_device_claim_buffer_mode(struct iio_dev *indio_dev)
+{
+	mutex_lock(&indio_dev->mlock);
+
+	if (iio_buffer_enabled(indio_dev))
+		return 0;
+
+	mutex_unlock(&indio_dev->mlock);
+	return -EBUSY;
+}
+EXPORT_SYMBOL_GPL(iio_device_claim_buffer_mode);
+
+/**
+ * iio_device_release_buffer_mode - releases claim on buffer mode
+ * @indio_dev:	the iio_dev associated with the device
+ *
+ * Release the claim. Device is no longer guaranteed to stay
+ * in buffer mode.
+ *
+ * Use with iio_device_claim_buffer_mode().
+ */
+void iio_device_release_buffer_mode(struct iio_dev *indio_dev)
+{
+	mutex_unlock(&indio_dev->mlock);
+}
+EXPORT_SYMBOL_GPL(iio_device_release_buffer_mode);
+
 /**
  * iio_device_get_current_mode() - helper function providing read-only access to
  *				   the @currentmode variable
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 0cac05d5ef1c3..9b43559e3acfd 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -575,6 +575,8 @@ int __devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev,
 int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp);
 int iio_device_claim_direct_mode(struct iio_dev *indio_dev);
 void iio_device_release_direct_mode(struct iio_dev *indio_dev);
+int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
+void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
 
 extern struct bus_type iio_bus_type;