linux-kernel - Re: [PATCH] driver core: auxiliary bus: add device creation helper

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Message-ID: <2024121048-latticed-etching-8961@gregkh>
Date: Tue, 10 Dec 2024 15:05:36 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: Dave Ertman <david.m.ertman@...el.com>, Ira Weiny <ira.weiny@...el.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Stephen Boyd <sboyd@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver core: auxiliary bus: add device creation helper

On Tue, Dec 10, 2024 at 02:43:12PM +0100, Jerome Brunet wrote:
> Add an function helper to create a device on the auxiliary bus.
> This should avoid having the same code repeated in the different drivers
> registering auxiliary devices.
> 
> Suggested-by: Stephen Boyd <sboyd@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
> The suggestion for this change was initially discussed here: [1]
> 
> I was not sure if the managed variant should return the auxiliary device or
> just the error. This initial version returns the auxiliary device, allowing
> it to be further (ab)used. Please let me know if you prefer to just return
> the error code instead.
> 
> Also the non managed variant of the helper is not exported but it could
> easily be, if necessary.
> 
> [1]: https://lore.kernel.org/linux-clk/df0a53ee859e450d84e81547099f5f36.sboyd@kernel.org
> ---
>  drivers/base/auxiliary.c      | 89 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/auxiliary_bus.h |  4 ++
>  2 files changed, 93 insertions(+)

We can't add new functions like this without a real user of it.  Please
submit that at the same time.

And are you ok with sharing the id range with multiple aux bus
implementations?


> 
> diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
> index afa4df4c5a3f371b91d8dd8c4325495d32ad1291..60ca3f0da329fb7f8e69ecdf703b505e7cf5085c 100644
> --- a/drivers/base/auxiliary.c
> +++ b/drivers/base/auxiliary.c
> @@ -385,6 +385,95 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
>  }
>  EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
>  
> +static DEFINE_IDA(auxiliary_device_ida);
> +
> +static void auxiliary_device_release(struct device *dev)
> +{
> +	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
> +
> +	ida_free(&auxiliary_device_ida, auxdev->id);
> +	kfree(auxdev);
> +}
> +
> +static struct auxiliary_device *auxiliary_device_create(struct device *dev,
> +							const char *name,
> +							void *platform_data)
> +{
> +	struct auxiliary_device *auxdev;
> +	int ret;
> +
> +	auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL);
> +	if (!auxdev)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = ida_alloc(&auxiliary_device_ida, GFP_KERNEL);
> +	if (ret < 0)
> +		goto auxdev_free;
> +
> +	auxdev->id = ret;
> +	auxdev->name = name;
> +	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)
> +		goto ida_free;
> +
> +	ret = __auxiliary_device_add(auxdev, dev->driver->name);
> +	if (ret) {
> +		auxiliary_device_uninit(auxdev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return auxdev;
> +
> +ida_free:
> +	ida_free(&auxiliary_device_ida, auxdev->id);
> +auxdev_free:
> +	kfree(auxdev);
> +	return ERR_PTR(ret);
> +}
> +
> +static void auxiliary_device_destroy(void *_auxdev)
> +{
> +	struct auxiliary_device *auxdev = _auxdev;
> +
> +	auxiliary_device_delete(auxdev);
> +	auxiliary_device_uninit(auxdev);
> +}
> +
> +/**
> + * devm_auxiliary_device_create - create a device on the auxiliary bus
> + * @dev: parent device
> + * @name: auxiliary bus driver name
> + * @platform_data: auxiliary bus device platform data
> + *
> + * Device managed helper to create an auxiliary bus device.
> + * The parent device KBUILD_MODNAME is automatically inserted before the

KBUILD_MODNAME doesn't make sense here, as that's the aux bus file.

thanks,

greg k-h