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>
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@ -313,6 +313,7 @@ struct iio_buffer_setup_ops {
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* @chrdev: [INTERN] associated character device
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* @groups: [INTERN] attribute groups
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* @groupcounter: [INTERN] index of next attribute group
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* @flags: [INTERN] file ops related flags including busy flag.
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**/
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struct iio_dev {
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int id;
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@ -344,6 +345,8 @@ struct iio_dev {
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#define IIO_MAX_GROUPS 6
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const struct attribute_group *groups[IIO_MAX_GROUPS + 1];
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int groupcounter;
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unsigned long flags;
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};
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/**
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@ -1083,9 +1083,18 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
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{
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struct iio_dev *indio_dev = container_of(inode->i_cdev,
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struct iio_dev, chrdev);
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unsigned int ret;
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if (test_and_set_bit(IIO_BUSY_BIT_POS, &indio_dev->flags))
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return -EBUSY;
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filp->private_data = indio_dev;
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return iio_chrdev_buffer_open(indio_dev);
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ret = iio_chrdev_buffer_open(indio_dev);
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if (ret < 0)
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clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
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return ret;
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}
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/**
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@ -1093,8 +1102,10 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
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**/
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static int iio_chrdev_release(struct inode *inode, struct file *filp)
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{
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iio_chrdev_buffer_release(container_of(inode->i_cdev,
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struct iio_dev, chrdev));
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struct iio_dev *indio_dev = container_of(inode->i_cdev,
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struct iio_dev, chrdev);
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iio_chrdev_buffer_release(indio_dev);
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clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
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return 0;
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}
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