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

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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39
drivers/iio/industrialio-core.c
View File

@ -25,6 +25,7 @@
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/debugfs.h>
#include <linux/mutex.h>
#include <linux/iio/iio.h>
#include "iio_core.h"
#include "iio_core_trigger.h"
@ -1375,6 +1376,44 @@ void devm_iio_device_unregister(struct device *dev, struct iio_dev *indio_dev)
}
EXPORT_SYMBOL_GPL(devm_iio_device_unregister);
/**
* iio_device_claim_direct_mode - Keep device in direct mode
* @indio_dev: the iio_dev associated with the device
*
* If the device is in direct mode it is guaranteed to stay
* that way until iio_device_release_direct_mode() is called.
*
* Use with iio_device_release_direct_mode()
*
* Returns: 0 on success, -EBUSY on failure
*/
int iio_device_claim_direct_mode(struct iio_dev *indio_dev)
{
mutex_lock(&indio_dev->mlock);
if (iio_buffer_enabled(indio_dev)) {
mutex_unlock(&indio_dev->mlock);
return -EBUSY;
}
return 0;
}
EXPORT_SYMBOL_GPL(iio_device_claim_direct_mode);
/**
* iio_device_release_direct_mode - releases claim on direct mode
* @indio_dev: the iio_dev associated with the device
*
* Release the claim. Device is no longer guaranteed to stay
* in direct mode.
*
* Use with iio_device_claim_direct_mode()
*/
void iio_device_release_direct_mode(struct iio_dev *indio_dev)
{
mutex_unlock(&indio_dev->mlock);
}
EXPORT_SYMBOL_GPL(iio_device_release_direct_mode);
subsys_initcall(iio_init);
module_exit(iio_exit);

2
include/linux/iio/iio.h
View File

@ -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;