linux-kernel - Re: [PATCH 4/6] PCI: of: Add an API to get the BDF for the device node

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Message-ID: <20250825224315.GA771834-robh@kernel.org>
Date: Mon, 25 Aug 2025 17:43:15 -0500
From: Rob Herring <robh@...nel.org>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Saravana Kannan <saravanak@...gle.com>, linux-pci@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
	Brian Norris <briannorris@...omium.org>
Subject: Re: [PATCH 4/6] PCI: of: Add an API to get the BDF for the device
 node

On Fri, Aug 22, 2025 at 07:57:41PM +0530, Manivannan Sadhasivam wrote:
> On Fri, Aug 22, 2025 at 08:51:47AM GMT, Rob Herring wrote:
> > On Tue, Aug 19, 2025 at 12:44:53PM +0530, Manivannan Sadhasivam wrote:
> > > Bus:Device:Function (BDF) numbers are used to uniquely identify a
> > > device/function on a PCI bus. Hence, add an API to get the BDF from the
> > > devicetree node of a device.
> > 
> > For FDT, the bus should always be 0. It doesn't make sense for FDT. The 
> > bus number in DT reflects how firmware configured the PCI buses, but 
> > there's no firmware configuration of PCI for FDT.
> 
> This API is targeted for DT platforms only, where it is used to uniquely
> identify a devfn. What should I do to make it DT specific and not FDT?

I don't understand. There are FDT and OF (actual OpenFirmware) 
platforms. I'm pretty sure you don't care about the latter.

Rob