[PATCH 4/8] staging:iio: Make sure a device is only opened once at a time
Lars-Peter Clausen
lars at metafoo.de
Mon Dec 19 14:23:45 UTC 2011
Our buffer implementation does not support multiple concurrent readers. So we
have to ensure that a device is only opened once at a time. So do the same thing
we do for the event fd and introduce a per device busy flag. The flag gets set
when opening the device and gets cleared when closing the device. If a open is
attempted while the busy flag is set we return -EBUSY.
Acked-by: Jonathan Cameron <jic23 at kernel.org>
Signed-off-by: Lars-Peter Clausen <lars at metafoo.de>
---
drivers/staging/iio/iio.h | 3 +++
drivers/staging/iio/industrialio-core.c | 17 ++++++++++++++---
2 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/iio/iio.h b/drivers/staging/iio/iio.h
index 45b6d75..be6ced3 100644
--- a/drivers/staging/iio/iio.h
+++ b/drivers/staging/iio/iio.h
@@ -313,6 +313,7 @@ struct iio_buffer_setup_ops {
* @chrdev: [INTERN] associated character device
* @groups: [INTERN] attribute groups
* @groupcounter: [INTERN] index of next attribute group
+ * @flags: [INTERN] file ops related flags including busy flag.
**/
struct iio_dev {
int id;
@@ -344,6 +345,8 @@ struct iio_dev {
#define IIO_MAX_GROUPS 6
const struct attribute_group *groups[IIO_MAX_GROUPS + 1];
int groupcounter;
+
+ unsigned long flags;
};
/**
diff --git a/drivers/staging/iio/industrialio-core.c b/drivers/staging/iio/industrialio-core.c
index 2eef85f..12d1576 100644
--- a/drivers/staging/iio/industrialio-core.c
+++ b/drivers/staging/iio/industrialio-core.c
@@ -1083,9 +1083,18 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
{
struct iio_dev *indio_dev = container_of(inode->i_cdev,
struct iio_dev, chrdev);
+ unsigned int ret;
+
+ if (test_and_set_bit(IIO_BUSY_BIT_POS, &indio_dev->flags))
+ return -EBUSY;
+
filp->private_data = indio_dev;
- return iio_chrdev_buffer_open(indio_dev);
+ ret = iio_chrdev_buffer_open(indio_dev);
+ if (ret < 0)
+ clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
+
+ return ret;
}
/**
@@ -1093,8 +1102,10 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
**/
static int iio_chrdev_release(struct inode *inode, struct file *filp)
{
- iio_chrdev_buffer_release(container_of(inode->i_cdev,
- struct iio_dev, chrdev));
+ struct iio_dev *indio_dev = container_of(inode->i_cdev,
+ struct iio_dev, chrdev);
+ iio_chrdev_buffer_release(indio_dev);
+ clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
return 0;
}
--
1.7.7.3
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