linux-kernel - Re: [PATCH v3 02/28] driver core: Rename get_dev_from_fwnode() wrapper to get_device_from

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Message-ID: <da8ada90-499f-41dc-808b-260d7a9229d3@kernel.org>
Date: Wed, 2 Jul 2025 20:51:33 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Rob Herring <robh@...nel.org>
Cc: Herve Codina <herve.codina@...tlin.com>, Andrew Lunn <andrew@...n.ch>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Peter Rosin <peda@...ntia.se>, Derek Kiernan <derek.kiernan@....com>,
 Dragan Cvetic <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>,
 Saravana Kannan <saravanak@...gle.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Mark Brown <broonie@...nel.org>, Len Brown <lenb@...nel.org>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Daniel Scally <djrscally@...il.com>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>, Wolfram Sang <wsa@...nel.org>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Davidlohr Bueso <dave@...olabs.net>, Dave Jiang <dave.jiang@...el.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>, linux-kernel@...r.kernel.org,
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
 linux-clk@...r.kernel.org, linux-i2c@...r.kernel.org,
 devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-spi@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-cxl@...r.kernel.org, Allan Nielsen <allan.nielsen@...rochip.com>,
 Horatiu Vultur <horatiu.vultur@...rochip.com>,
 Steen Hegelund <steen.hegelund@...rochip.com>,
 Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3 02/28] driver core: Rename get_dev_from_fwnode()
 wrapper to get_device_from_fwnode()

On 6/27/25 4:18 PM, Rob Herring wrote:
> On Fri, Jun 13, 2025 at 03:47:42PM +0200, Herve Codina wrote:
>> get_dev_from_fwnode() calls get_device() and so it acquires a reference
>> on the device returned.
>>
>> In order to be more obvious that this wrapper is a get_device() variant,
>> rename it to get_device_from_fwnode().
>>
>> Suggested-by: Mark Brown <broonie@...nel.org>
>> Link: https://lore.kernel.org/lkml/CAGETcx97QjnjVR8Z5g0ndLHpK96hLd4aYSV=iEkKPNbNOccYmA@mail.gmail.com/
>> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>> Reviewed-by: Saravana Kannan <saravanak@...gle.com>
>> Reviewed-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
>> ---
>>   drivers/base/core.c | 14 +++++++-------
>>   1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index cbc0099d8ef2..36ccee91ba9a 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -1881,7 +1881,7 @@ static void fw_devlink_unblock_consumers(struct device *dev)
>>   	device_links_write_unlock();
>>   }
>>   
>> -#define get_dev_from_fwnode(fwnode)	get_device((fwnode)->dev)
>> +#define get_device_from_fwnode(fwnode)	get_device((fwnode)->dev)
> 
> In patch 3, you add the same define. Is there some reason to not move it
> to a header?

AFAIK, the struct device pointer in struct fwnode_handle is not backed by a
reference count, which means that it's the callers responsibility to ensure that
it's guaranteed that the pointer in struct fwnode_handle is still valid.

Besides some driver-core internals the pointer shouldn't be used, and hence this
helper shouldn't be available through a public header.