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staging:iio: Make sure a device is only opened once at a time

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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@kernel.org>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Lars-Peter Clausen 2011-12-19 15:23:45 +01:00 committed by Greg Kroah-Hartman
parent e38c79e082
commit bb01443e2c
2 changed files with 17 additions and 3 deletions
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3
drivers/staging/iio/iio.h
View file

@ -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;
};
/**

17
drivers/staging/iio/industrialio-core.c
View file

@ -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;
}