Re: [PATCH net-next 07/10] net: phy: switch to using class_find_device_by_fwnode()

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Andrew Lunn <andrew@lunn.ch>, Andrew Lunn <andrew+netdev@lunn.ch>,
	 "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>, Vinod Koul <vkoul@kernel.org>,
	 Neil Armstrong <neil.armstrong@linaro.org>,
	Mark Brown <broonie@kernel.org>,
	 Liam Girdwood <lgirdwood@gmail.com>, Lee Jones <lee@kernel.org>,
	Pavel Machek <pavel@kernel.org>,  Peter Rosin <peda@axentia.se>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	 Moritz Fischer <mdf@kernel.org>, Xu Yilun <yilun.xu@intel.com>,
	Tom Rix <trix@redhat.com>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	 Danilo Krummrich <dakr@kernel.org>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	 linux-phy@lists.infradead.org, linux-spi@vger.kernel.org,
	linux-leds@vger.kernel.org,  linux-fpga@vger.kernel.org,
	driver-core@lists.linux.dev
Subject: Re: [PATCH net-next 07/10] net: phy: switch to using class_find_device_by_fwnode()
Date: Mon, 23 Mar 2026 11:33:36 -0700	[thread overview]
Message-ID: <acGGWTmSMuc5h3Od@google.com> (raw)
In-Reply-To: <acEBCBgMV3RrGKiU@shell.armlinux.org.uk>

On Mon, Mar 23, 2026 at 08:59:52AM +0000, Russell King (Oracle) wrote:
> On Sun, Mar 22, 2026 at 10:17:15PM -0700, Dmitry Torokhov wrote:
> > On Mon, Mar 23, 2026 at 03:54:09AM +0100, Andrew Lunn wrote:
> > > > -	d = class_find_device_by_of_node(&mdio_bus_class, mdio_bus_np);
> > > > +	d = class_find_device_by_fwnode(&mdio_bus_class,
> > > > +					of_fwnode_handle(mdio_bus_np));
> > > 
> > > When you look at this, why is it better?
> > 
> > I think we should move as much as possible towards firmware-agnostic
> > APIs and use fwnode_handle instead of device_node or software_node or
> > ACPI companion. To discourage this I think we better remove
> > firmware-specific APIs where we have firmware-agnostic ones and
> > eventually clean up drivers that use OF- or ACPI-specific APIs.
> 
> Basically, no. This is wrong.
> 
> It may sound like a good goal, but there's an underlying issue. This
> goal assumes that the firmware description in OF and ACPI are
> indentical.

If they are different then drivers will make allowance for this, like
I2C core or SPI core does. But most of the modern drivers use
firmware-agnostic APIs (device_property_*()).

ACPI has allowance for device tree properties (via PRP0001 HID
entries), and drivers should work with them.

> 
> Sure, looking up devices by fwnode handle makes sense, but looking up
> anything that is described in firmware is not suitable for this kind
> of conversion, because in doing so, you effectively "port" the DT
> bindings to ACPI, and it may not be suitable for ACPI.
> 
> So, please don't make wholesale changes that transfer the DT bindings
> into ACPI.
> 

I am not "transferring" anything, but I want to make sure the code works
even if we augment OF with software nodes or if DT properties are used
in ACPI.

Thanks.

-- 
Dmitry