linux-kernel - Re: [PATCH v8 0/5] PCI: endpoint: BAR subrange mapping support

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Message-ID: <aXHfUyd0EPFnoVBO@ryzen>
Date: Thu, 22 Jan 2026 09:45:13 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Koichiro Den <den@...inux.co.jp>
Cc: Manivannan Sadhasivam <mani@...nel.org>, bhelgaas@...gle.com,
	kwilczynski@...nel.org, frank.li@....com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/5] PCI: endpoint: BAR subrange mapping support

Hello Koichiro,

On Thu, Jan 22, 2026 at 10:52:31AM +0900, Koichiro Den wrote:
> > 
> > In this series you didn't add a consumer of this subrange mapping, which I
> > believe is the epf-vntb driver [1]. Even so I don't see a justification of why
> > the BAR needs to be split into multiple subranges. Can you explain that?
> 
> Yes, the first consumer I have in mind is epf-vntb / remote eDMA-backed NTB
> work referenced in [1].

Another consumer in your RFC series is pci-epf-test, specifically:
[RFC PATCH v4 35/38] PCI: endpoint: pci-epf-test: Add pci_epf_test_next_free_bar() helper
[RFC PATCH v4 36/38] PCI: endpoint: pci-epf-test: Add remote eDMA-backed mode
[RFC PATCH v4 37/38] misc: pci_endpoint_test: Add remote eDMA transfer test mode
[RFC PATCH v4 38/38] selftests: pci_endpoint: Add remote eDMA transfer coverage

where the pci-epf-test exports the eDMA registers (using subranges) over a
BAR, and then in the host side driver, calls dw_edma_probe() on this subrange
and uses the host side driver to control the eDMA residing in the endpoint.

Most of your patches in [RFC PATCH v4 35/38] have NTB prefix.

Would it not be possible to simply include patches 35-38 in this series,
so we actually have a consumer, or do you need some other patches as well?

E.g., perhaps
[RFC PATCH v4 01/38] dmaengine: dw-edma: Export helper to get integrated register window

Would also be required?



Kind regards,
Niklas