[PATCH 01/10] iio: locking: introduce __cleanup() based direct mode claiming infrastructure

[Jonathan Cameron <jic23@kernel.org>]

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Allows use of:

       iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
       }

to automatically call iio_device_release_direct_mode() based on scope.
Typically seen in combination with local device specific locks which
are already have automated cleanup options via guard(mutex)(&st->lock)
and scoped_guard(). Using both together allows most error handling to
be automated.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
Since RFC:
 - Drop the IS_ERR() protection in iio_device_release_direct_mode()
   as nothing in this new infrastructure results in this function
   being passed an error pointer.
 - Add some blank lines to make the header slightly easier to read.
---
 include/linux/iio/iio.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index c5b36d2c1e73..28e78af3614b 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -9,6 +9,7 @@
 
 #include <linux/device.h>
 #include <linux/cdev.h>
+#include <linux/cleanup.h>
 #include <linux/slab.h>
 #include <linux/iio/types.h>
 /* IIO TODO LIST */
@@ -638,6 +639,30 @@ 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);
+
+/* This autocleanup logic is normally used via iio_claim_direct_scoped */
+DEFINE_GUARD(iio_claim_direct, struct iio_dev *, iio_device_claim_direct_mode(_T),
+	     iio_device_release_direct_mode(_T))
+
+DEFINE_GUARD_COND(iio_claim_direct, _try, ({
+			struct iio_dev *dev;
+			int d = iio_device_claim_direct_mode(_T);
+
+			if (d < 0)
+				dev = NULL;
+			else
+				dev = _T;
+			dev;
+		}))
+
+/**
+ * iio_device_claim_direct_scoped() - Scoped call to iio_device_claim_direct.
+ * @fail: What to do on failure to claim device.
+ * @iio_dev: Pointer to the IIO devices structure
+ */
+#define iio_device_claim_direct_scoped(fail, iio_dev) \
+	scoped_cond_guard(iio_claim_direct_try, fail, iio_dev)
+
 int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
 void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
 
-- 
2.43.0