[PATCH v4 1/8] driver core: auxiliary bus: add device creation helpers

[Dmitry Baryshkov]

On Tue, Feb 18, 2025 at 08:29:46PM +0100, Jerome Brunet wrote:
> Add helper functions to create a device on the auxiliary bus.
> 
> This is meant for fairly simple usage of the auxiliary bus, to avoid having
> the same code repeated in the different drivers.
> 
> Suggested-by: Stephen Boyd <sboyd at kernel.org>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Signed-off-by: Jerome Brunet <jbrunet at baylibre.com>
> ---
>  drivers/base/auxiliary.c      | 108 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/auxiliary_bus.h |  17 +++++++
>  2 files changed, 125 insertions(+)
> 
> diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
> index afa4df4c5a3f371b91d8dd8c4325495d32ad1291..a6d46c2759be81a0739f07528d5959c2a76eb8a8 100644
> --- a/drivers/base/auxiliary.c
> +++ b/drivers/base/auxiliary.c
> @@ -385,6 +385,114 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
>  }
>  EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
>  
> +static void auxiliary_device_release(struct device *dev)
> +{
> +	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
> +
> +	kfree(auxdev);
> +}
> +
> +/**
> + * auxiliary_device_create - create a device on the auxiliary bus
> + * @dev: parent device
> + * @modname: module name used to create the auxiliary driver name.
> + * @devname: auxiliary bus device name
> + * @platform_data: auxiliary bus device platform data
> + * @id: auxiliary bus device id
> + *
> + * Helper to create an auxiliary bus device.
> + * The device created matches driver 'modname.devname' on the auxiliary bus.
> + */
> +struct auxiliary_device *auxiliary_device_create(struct device *dev,
> +						 const char *modname,
> +						 const char *devname,
> +						 void *platform_data,
> +						 int id)
> +{
> +	struct auxiliary_device *auxdev;
> +	int ret;
> +
> +	auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL);
> +	if (!auxdev)
> +		return NULL;
> +
> +	auxdev->id = id;
> +	auxdev->name = devname;
> +	auxdev->dev.parent = dev;
> +	auxdev->dev.platform_data = platform_data;
> +	auxdev->dev.release = auxiliary_device_release;
> +	device_set_of_node_from_dev(&auxdev->dev, dev);
> +
> +	ret = auxiliary_device_init(auxdev);
> +	if (ret) {
> +		kfree(auxdev);
> +		return NULL;
> +	}
> +
> +	ret = __auxiliary_device_add(auxdev, modname);
> +	if (ret) {

This loses possible error return values from __auxiliary_device_add().
I'd suggest to return ERR_PTR(ret) here and in the
auxiliary_device_init() chunks and ERR_PTR(-ENOMEM) in case of kzalloc()
failure.

> +		/*
> +		 * It may look odd but auxdev should not be freed here.
> +		 * auxiliary_device_uninit() calls device_put() which call
> +		 * the device release function, freeing auxdev.
> +		 */
> +		auxiliary_device_uninit(auxdev);
> +		return NULL;
> +	}
> +
> +	return auxdev;
> +}
> +EXPORT_SYMBOL_GPL(auxiliary_device_create);
> +

-- 
With best wishes
Dmitry