linux-kernel - Re: [PATCH v3 18/28] of: property: Allow fw_devlink device-tree on x86 when PCI device-tree node creation is enabled

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Message-ID: <aF7H4-toeb7Ouz3d@smile.fi.intel.com>
Date: Fri, 27 Jun 2025 19:33:39 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
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>,
	Danilo Krummrich <dakr@...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>,
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	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>,
	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>,
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	Dave Jiang <dave.jiang@...el.com>,
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	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 18/28] of: property: Allow fw_devlink device-tree on
 x86 when PCI device-tree node creation is enabled

On Fri, Jun 27, 2025 at 11:22:45AM -0500, Rob Herring wrote:
> On Fri, Jun 13, 2025 at 03:47:58PM +0200, Herve Codina wrote:

...

> > -	if (IS_ENABLED(CONFIG_X86))
> > +	if (IS_ENABLED(CONFIG_X86) && !IS_ENABLED(CONFIG_PCI_DYNAMIC_OF_NODES))
> 
> I really want CONFIG_PCI_DYNAMIC_OF_NODES to go away at some point, not 
> add more users. 
> 
> I think this should instead check for specific platforms not with 
> kconfig symbols but DT properties. For ce4100, you can just check the 
> root compatible string. For OLPC, there isn't a root compatible (in the 
> DT I have). You could check for /architecture == OLPC instead. There's 
> some virtualization guests using DT now too. I would think their DT's 
> are simple enough to avoid any fw_devlink issues. 

I don't think this is good approach. The above check is more reliable in my
opinion.

> Alternatively, we could perhaps make x86 fw_devlink default off

For my (little) knowledge I believe this is not feasible anymore.
Some x86 code (drivers) relies on fw_devlink nowadays. But take
this with grain of salt, I may be way mistaken.

> and then enable it only when you create nodes. Maybe it has to be restricted
> a sub tree of the DT to avoid any later interactions if devices are unbound
> and rebound. Not a fully fleshed out idea...

-- 
With Best Regards,
Andy Shevchenko