[PATCH v4 4/7] iio: core: Add cleanup.h support for iio_device_claim_*()

[Kurt Borja <kuurtb@gmail.com>]

Add guard classes for iio_device_claim_*() conditional locks. This will
aid drivers write safer and cleaner code when dealing with some common
patterns.

These classes are not meant to be used directly by drivers (hence the
__priv__ prefix). Instead, documented wrapper macros are provided to
enforce the use of ACQUIRE() or guard() semantics and avoid the
problematic scoped guard.

Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Kurt Borja <kuurtb@gmail.com>
---
 include/linux/iio/iio.h | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index fa671e120e95..4a0a77fcfa8d 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -10,6 +10,7 @@
 #include <linux/align.h>
 #include <linux/device.h>
 #include <linux/cdev.h>
+#include <linux/cleanup.h>
 #include <linux/compiler_types.h>
 #include <linux/minmax.h>
 #include <linux/slab.h>
@@ -740,6 +741,70 @@ static inline bool iio_device_try_claim_buffer_mode(struct iio_dev *indio_dev)
  */
 #define iio_device_release_buffer_mode(indio_dev) __iio_dev_mode_unlock(indio_dev)
 
+/*
+ * These classes are not meant to be used directly by drivers (hence the
+ * __priv__ prefix). Instead, documented wrapper macros are provided below to
+ * enforce the use of ACQUIRE() or guard() semantics and avoid the problematic
+ * scoped guard variants.
+ */
+DEFINE_GUARD(__priv__iio_dev_mode_lock, struct iio_dev *,
+	     __iio_dev_mode_lock(_T), __iio_dev_mode_unlock(_T));
+DEFINE_GUARD_COND(__priv__iio_dev_mode_lock, _try_direct,
+		  iio_device_claim_direct(_T));
+
+/**
+ * IIO_DEV_ACQUIRE_DIRECT_MODE(dev, var) - Tries to acquire the direct mode
+ *					   lock with automatic release
+ * @dev: IIO device instance
+ * @claim: Variable identifier to store acquire result
+ *
+ * Tries to acquire the direct mode lock with cleanup ACQUIRE() semantics and
+ * automatically releases it at the end of the scope. It most be always paired
+ * with IIO_DEV_ACQUIRE_ERR(), for example (notice the scope braces)::
+ *
+ *	switch() {
+ *	case IIO_CHAN_INFO_RAW: {
+ *		IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
+ *		if (IIO_DEV_ACQUIRE_FAILED(claim))
+ *			return -EBUSY;
+ *
+ *		...
+ *	}
+ *	case IIO_CHAN_INFO_SCALE:
+ *		...
+ *	...
+ *	}
+ *
+ * Context: Can sleep
+ */
+#define IIO_DEV_ACQUIRE_DIRECT_MODE(dev, claim) \
+	ACQUIRE(__priv__iio_dev_mode_lock_try_direct, claim)(dev)
+
+/**
+ * IIO_DEV_ACQUIRE_FAILED() - ACQUIRE_ERR() wrapper
+ * @claim: The claim variable passed to IIO_DEV_ACQUIRE_*_MODE()
+ *
+ * Return: true if failed to acquire the mode, otherwise false.
+ */
+#define IIO_DEV_ACQUIRE_FAILED(claim) \
+	ACQUIRE_ERR(__priv__iio_dev_mode_lock_try_direct, &(claim))
+
+/**
+ * IIO_DEV_GUARD_CURRENT_MODE - Acquires the mode lock with automatic release
+ * @dev: IIO device instance
+ *
+ * Acquires the mode lock with cleanup guard() semantics. It is usually paired
+ * with iio_buffer_enabled().
+ *
+ * This should *not* be used to protect internal driver state and it's use in
+ * general is *strongly* discouraged. Use any of the IIO_DEV_ACQUIRE_*_MODE()
+ * variants.
+ *
+ * Context: Can sleep
+ */
+#define IIO_DEV_GUARD_CURRENT_MODE(dev) \
+	guard(__priv__iio_dev_mode_lock)(dev)
+
 extern const struct bus_type iio_bus_type;
 
 /**

-- 
2.52.0