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

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Message-ID: <crtrciitrlqkxh5mxvnbdjy6zoxny5onse7xgbw7biozg6myux@grp3ketgl2uh>
Date: Wed, 19 Feb 2025 11:06:02 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	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>, 
	Danilo Krummrich <dakr@...nel.org>, Conor Dooley <conor.dooley@...rochip.com>, 
	Daire McNamara <daire.mcnamara@...rochip.com>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Douglas Anderson <dianders@...omium.org>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Hans de Goede <hdegoede@...hat.com>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>, Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
	Gregory CLEMENT <gregory.clement@...tlin.com>, Théo Lebrun <theo.lebrun@...tlin.com>, 
	Michael Turquette <mturquette@...libre.com>, Abel Vesa <abelvesa@...nel.org>, Peng Fan <peng.fan@....com>, 
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, 
	Kevin Hilman <khilman@...libre.com>, Martin Blumenstingl <martin.blumenstingl@...glemail.com>, 
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, dri-devel@...ts.freedesktop.org, 
	platform-driver-x86@...r.kernel.org, linux-mips@...r.kernel.org, linux-clk@...r.kernel.org, 
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v4 1/8] driver core: auxiliary bus: add device creation
 helpers

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@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.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