iio: core: wrap iio device & buffer into struct for character devices

In order to keep backwards compatibility with the current chardev
mechanism, and in order to add support for multiple buffers per IIO device,
we need to pass both the IIO device & IIO buffer to the chardev.

This is particularly needed for the iio_buffer_read_outer() function, where
we need to pass another buffer object than 'indio_dev->buffer'.

Since we'll also open some chardevs via anon inodes, we can pass extra
buffers in that function by assigning another object to the
iio_dev_buffer_pair object.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-17-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index b8b149ccecef..b96acfe13e92 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1705,13 +1705,24 @@ 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);
+	struct iio_dev_buffer_pair *ib;
 
 	if (test_and_set_bit(IIO_BUSY_BIT_POS, &indio_dev->flags))
 		return -EBUSY;
 
 	iio_device_get(indio_dev);
 
-	filp->private_data = indio_dev;
+	ib = kmalloc(sizeof(*ib), GFP_KERNEL);
+	if (!ib) {
+		iio_device_put(indio_dev);
+		clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
+		return -ENOMEM;
+	}
+
+	ib->indio_dev = indio_dev;
+	ib->buffer = indio_dev->buffer;
+
+	filp->private_data = ib;
 
 	return 0;
 }
@@ -1725,8 +1736,10 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
  */
 static int iio_chrdev_release(struct inode *inode, struct file *filp)
 {
+	struct iio_dev_buffer_pair *ib = filp->private_data;
 	struct iio_dev *indio_dev = container_of(inode->i_cdev,
 						struct iio_dev, chrdev);
+	kfree(ib);
 	clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
 	iio_device_put(indio_dev);
 
@@ -1748,7 +1761,8 @@ void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h)
 
 static long iio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
-	struct iio_dev *indio_dev = filp->private_data;
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_dev *indio_dev = ib->indio_dev;
 	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 	struct iio_ioctl_handler *h;
 	int ret = -ENODEV;