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iio: core: implement iio_device_{claim|release}_direct_mode()

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It is often the case that the driver wants to be sure a device stays
in direct mode while it is executing a task or series of tasks.  To
accomplish this today, the driver performs this sequence: 1) take the
device state lock, 2) verify it is not in a buffered mode, 3) execute
some tasks, and 4) release that lock.

This patch introduces a pair of helper functions that simplify these
steps and make it more semantically expressive.

iio_device_claim_direct_mode()
        If the device is not in any buffered mode it is guaranteed
        to stay that way until iio_release_direct_mode() is called.

iio_device_release_direct_mode()
        Release the claim. Device is no longer guaranteed to stay
        in direct mode.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Alison Schofield
2016-03-09 11:30:12 -08:00
committed by Jonathan Cameron
parent e8731180fb
commit 08a3380551
2 changed files with 41 additions and 0 deletions
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include/linux/iio/iio.h
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@@ -527,6 +527,8 @@ void iio_device_unregister(struct iio_dev *indio_dev);
int devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev);
void devm_iio_device_unregister(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);
extern struct bus_type iio_bus_type;