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[93.41.3.120]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43629745f7asm25073238f8f.33.2026.02.09.10.16.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Feb 2026 10:16:46 -0800 (PST) From: Andrea della Porta X-Google-Original-From: Andrea della Porta Date: Mon, 9 Feb 2026 19:19:34 +0100 To: Rob Herring Cc: Herve Codina , Andrea della Porta , Bjorn Helgaas , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, mbrugger@suse.com, guillaume.gardet@arm.com, tiwai@suse.com, Lizhi Hou Subject: Re: [PATCH v2] PCI: of: Downgrade error message on missing of_root node Message-ID: References: <20251106182708.03cfb6c6@bootlin.com> <20251106175016.GA1960490@bhelgaas> <20251107125828.18a034de@bootlin.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Hi, On 07:58 Fri 05 Dec , Rob Herring wrote: > On Fri, Nov 7, 2025 at 5:58 AM Herve Codina wrote: > > > > Hi Andrea, Bjorn, > > > > On Fri, 7 Nov 2025 10:32:35 +0100 > > Andrea della Porta wrote: > > > > > Hi Bjorn, > > > > > > On 11:50 Thu 06 Nov , Bjorn Helgaas wrote: > > > > On Thu, Nov 06, 2025 at 06:27:08PM +0100, Herve Codina wrote: > > > > > On Thu, 6 Nov 2025 16:21:47 +0100 > > > > > Andrea della Porta wrote: > > > > > > On 13:18 Thu 06 Nov , Herve Codina wrote: > > > > > > > On Thu, 6 Nov 2025 12:04:07 +0100 > > > > > > > Andrea della Porta wrote: > > > > > > > > On 18:23 Wed 05 Nov , Bjorn Helgaas wrote: > > > > > > > > > On Wed, Nov 05, 2025 at 07:33:40PM +0100, Andrea della Porta wrote: > > > > Patch at https://lore.kernel.org/r/955bc7a9b78678fad4b705c428e8b45aeb0cbf3c.1762367117.git.andrea.porta@suse.com, > > > > added back for reference: > > > > > > > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > > > > index 3579265f1198..872c36b195e3 100644 > > > > --- a/drivers/pci/of.c > > > > +++ b/drivers/pci/of.c > > > > @@ -775,7 +775,7 @@ void of_pci_make_host_bridge_node(struct pci_host_bridge *bridge) > > > > > > > > /* Check if there is a DT root node to attach the created node */ > > > > if (!of_root) { > > > > - pr_err("of_root node is NULL, cannot create PCI host bridge node\n"); > > > > + pr_info("Missing DeviceTree, cannot create PCI host bridge node\n"); > > > > return; > > > > } > > > > > > > > > > > > > > When CONFIG_PCI_DYNAMIC_OF_NODES is enabled, an error > > > > > > > > > > message is generated if no 'of_root' node is defined. > > > > > > > > > > > > > > > > > > > > On DT-based systems, this cannot happen as a root DT node > > > > > > > > > > is always present. On ACPI-based systems, this is not a > > > > > > > > > > true error because a DT is not used. > > > > > > > > > > > > > > > > > > > > Downgrade the pr_err() to pr_info() and reword the message > > > > > > > > > > text to be less context specific. > > > > > > > > > > > > > > > > > > of_pci_make_host_bridge_node() is called in the very generic > > > > > > > > > pci_register_host_bridge() path. Does that mean every boot > > > > > > > > > of a kernel with CONFIG_PCI_DYNAMIC_OF_NODES on a non-DT > > > > > > > > > system will see this message? > > > > > > > > > > > > > > > > This is the case, indeed. That's why downgrading to info seems > > > > > > > > sensible. > > > > > > > > > > > > > > > > > This message seems like something that will generate user > > > > > > > > > questions. Or is this really an error, and we were supposed > > > > > > > > > to have created of_root somewhere but it failed? If so, I > > > > > > > > > would expect a message where the of_root creation failed. > > > > > > > > I think we should just remove the message completely. I don't want > > > > users to enable CONFIG_PCI_DYNAMIC_OF_NODES out of curiosity or > > > > willingness to test, and then ask about this message. > > No, please keep it. Anyone that enables CONFIG_PCI_DYNAMIC_OF_NODES > should know what they are doing. I was thinking it should be hidden > behind EXPERT perhaps. Ok, so it seems that this message is there to stay, can we just turn it to a warning to relieve pressure? Thanks, Andrea > > > > > > > Agreed. This would be the easy solution, the other being creating the > > > empty DT so that the message will never be printed. But this require some > > > careful thought. The latter solution will be needed if we'll ever want to > > > make drivers like RP1 or lan96xx (which uses the runtime overlay) to work. > > > > > > > > > > > "You can avoid the message by also enabling CONFIG_OF_EARLY_FLATTREE" > > > > is not a very satisfactory answer. > > > > > > Unfortunately this would work on x86, but not on arm. And who knows on > > > other platforms. > > > > > > > > > > > A message at the point of *needing* this, i.e., when loading an > > > > overlay fails for lack of this dynamic DT, is fine. > > > > > > It seems fine to me. > > > > > > > Ok, even if I would prefer having an empty (or not) of_node available on all > > platforms, what is proposed makes sense especially in regards to potential > > users questions. > > Having a DT always available was the original intent, but the arm64 > maintainers resisted so that's a fight for another day when someone > really wants to use this on an ACPI system. Now riscv has done the > same thing unfortunately. > > Rob