Re: [PATCH 7/9] iio: core: move @chrdev from struct iio_dev to struct iio_dev_opaque

[Alexandru Ardelean <ardeleanalex@gmail.com>]

On Mon, Apr 26, 2021 at 8:50 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>
> No reason for this to be exposed to the drivers, so lets move it to the
> opaque structure.

Even though this looks straightforward, I am paranoid about it.
Mostly because of all the chardev juggling that I tried.

Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>

>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  drivers/iio/industrialio-core.c | 20 +++++++++++---------
>  include/linux/iio/iio-opaque.h  |  2 ++
>  include/linux/iio/iio.h         |  2 --
>  3 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index f3b38d69b7e1..6fbe29f0b1de 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1715,8 +1715,9 @@ EXPORT_SYMBOL_GPL(devm_iio_device_alloc);
>   **/
>  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_opaque *iio_dev_opaque =
> +               container_of(inode->i_cdev, struct iio_dev_opaque, chrdev);
> +       struct iio_dev *indio_dev = &iio_dev_opaque->indio_dev;
>         struct iio_dev_buffer_pair *ib;
>
>         if (test_and_set_bit(IIO_BUSY_BIT_POS, &indio_dev->flags))
> @@ -1749,8 +1750,9 @@ 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);
> +       struct iio_dev_opaque *iio_dev_opaque =
> +               container_of(inode->i_cdev, struct iio_dev_opaque, chrdev);
> +       struct iio_dev *indio_dev = &iio_dev_opaque->indio_dev;
>         kfree(ib);
>         clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
>         iio_device_put(indio_dev);
> @@ -1901,19 +1903,19 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
>                 indio_dev->setup_ops = &noop_ring_setup_ops;
>
>         if (iio_dev_opaque->attached_buffers_cnt)
> -               cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
> +               cdev_init(&iio_dev_opaque->chrdev, &iio_buffer_fileops);
>         else if (iio_dev_opaque->event_interface)
> -               cdev_init(&indio_dev->chrdev, &iio_event_fileops);
> +               cdev_init(&iio_dev_opaque->chrdev, &iio_event_fileops);
>
>         if (iio_dev_opaque->attached_buffers_cnt || iio_dev_opaque->event_interface) {
>                 indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), iio_dev_opaque->id);
> -               indio_dev->chrdev.owner = this_mod;
> +               iio_dev_opaque->chrdev.owner = this_mod;
>         }
>
>         /* assign device groups now; they should be all registered now */
>         indio_dev->dev.groups = iio_dev_opaque->groups;
>
> -       ret = cdev_device_add(&indio_dev->chrdev, &indio_dev->dev);
> +       ret = cdev_device_add(&iio_dev_opaque->chrdev, &indio_dev->dev);
>         if (ret < 0)
>                 goto error_unreg_eventset;
>
> @@ -1940,7 +1942,7 @@ void iio_device_unregister(struct iio_dev *indio_dev)
>         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
>         struct iio_ioctl_handler *h, *t;
>
> -       cdev_device_del(&indio_dev->chrdev, &indio_dev->dev);
> +       cdev_device_del(&iio_dev_opaque->chrdev, &indio_dev->dev);
>
>         mutex_lock(&iio_dev_opaque->info_exist_lock);
>
> diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h
> index 538b4b5ef1a9..2f8ef5d15a66 100644
> --- a/include/linux/iio/iio-opaque.h
> +++ b/include/linux/iio/iio-opaque.h
> @@ -24,6 +24,7 @@
>   * @legacy_scan_el_group:      attribute group for legacy scan elements attribute group
>   * @legacy_buffer_group:       attribute group for legacy buffer attributes group
>   * @scan_index_timestamp:      cache of the index to the timestamp
> + * @chrdev:                    associated character device
>   * @debugfs_dentry:            device specific debugfs dentry
>   * @cached_reg_addr:           cached register address for debugfs reads
>   * @read_buf:                  read buffer to be used for the initial reg read
> @@ -49,6 +50,7 @@ struct iio_dev_opaque {
>         struct attribute_group          legacy_buffer_group;
>
>         unsigned int                    scan_index_timestamp;
> +       struct cdev                     chrdev;
>
>  #if defined(CONFIG_DEBUG_FS)
>         struct dentry                   *debugfs_dentry;
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index a12bbd8b1e74..586e2dc4fbf3 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -512,7 +512,6 @@ struct iio_buffer_setup_ops {
>   * @clock_id:          [INTERN] timestamping clock posix identifier
>   * @setup_ops:         [DRIVER] callbacks to call before and after buffer
>   *                     enable/disable
> - * @chrdev:            [INTERN] associated character device
>   * @flags:             [INTERN] file ops related flags including busy flag.
>   * @priv:              [DRIVER] reference to driver's private information
>   *                     **MUST** be accessed **ONLY** via iio_priv() helper
> @@ -542,7 +541,6 @@ struct iio_dev {
>         const struct iio_info           *info;
>         clockid_t                       clock_id;
>         const struct iio_buffer_setup_ops       *setup_ops;
> -       struct cdev                     chrdev;
>
>         unsigned long                   flags;
>         void                            *priv;
> --
> 2.31.1
>