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Message-ID: <eskvhtljnrkhm6vmqy52gkweexj3tcethejeywcoib4la72jcl@ojuqcazpvht4>
Date: Wed, 19 Feb 2025 14:08:22 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jerome Brunet <jbrunet@...libre.com>,
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 Wed, Feb 19, 2025 at 11:13:14AM +0100, Greg Kroah-Hartman wrote:
> On Wed, Feb 19, 2025 at 11:06:02AM +0200, Dmitry Baryshkov wrote:
> > 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().
>
> Why does that really matter?
At the very least the caller (or caller of a caller) can call
dev_err_probe() or dev_err("%pe"). With the current implementation as
everybody maps NULL to -ENOMEM the error message will be cryptic.
Or just having a cryptic value in the logs.
> > 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.
>
> Will the caller do something different based on the error value here?
> All we care is that this worked or not, the specific error isn't going
> to matter for device creation like this.
The caller might not, the developer might.
--
With best wishes
Dmitry
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