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

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>

diff --git a/drivers/staging/iio/iio.h b/drivers/staging/iio/iio.h
index 45b6d759c2e7f68098fe8966ef03bfbdab9798f2..be6ced31f65e6dd057c47419799432619d69aceb 100644 (file)
--- 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 2eef85fa38c7957d7fb2458ce9e61251eac9fb82..12d1576a076693b5a04017165f1db6f6e33d6558 100644 (file)
--- 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;
 }