Re: [PATCH v2 2/4] serdev: add private data to serdev_device

["Danilo Krummrich" <dakr@kernel.org>]

On Fri Mar 6, 2026 at 8:35 PM CET, Markus Probst wrote:
> Add private data to `struct serdev_device`, as it is required by the
> rust abstraction added in the following commit
> (rust: add basic serial device bus abstractions).
>
> Signed-off-by: Markus Probst <markus.probst@posteo.de>
> ---
>  include/linux/serdev.h | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> index 5654c58eb73c..b591af23faf0 100644
> --- a/include/linux/serdev.h
> +++ b/include/linux/serdev.h
> @@ -33,12 +33,13 @@ struct serdev_device_ops {
>  
>  /**
>   * struct serdev_device - Basic representation of an serdev device
> - * @dev:	Driver model representation of the device.
> - * @nr:		Device number on serdev bus.
> - * @ctrl:	serdev controller managing this device.
> - * @ops:	Device operations.
> - * @write_comp	Completion used by serdev_device_write() internally
> - * @write_lock	Lock to serialize access when writing data
> + * @dev:	 Driver model representation of the device.
> + * @nr:		 Device number on serdev bus.
> + * @ctrl:	 serdev controller managing this device.
> + * @ops:	 Device operations.
> + * @write_comp	 Completion used by serdev_device_write() internally
> + * @write_lock	 Lock to serialize access when writing data
> + * @private_data Private data for the device driver.

I think this is a bit misleading, as the driver's device private data is stored
in the embedded struct device. This seems to be more about having a place to
store private data of the Rust abstraction.

So, you may want to name this something along the lines of rust_private_data.
Additionally, you should make it very clear that this field must not be used by
drivers directly (i.e. C drivers could easily be tempted to abuse this).

>   */
>  struct serdev_device {
>  	struct device dev;
> @@ -47,6 +48,7 @@ struct serdev_device {
>  	const struct serdev_device_ops *ops;
>  	struct completion write_comp;
>  	struct mutex write_lock;
> +	void *private_data;
>  };
>  
>  static inline struct serdev_device *to_serdev_device(struct device *d)
>
> -- 
> 2.52.0