linux-kernel - Re: [PATCH 2/5] PCI: dwc: Add new APIs to remove standard and extended Capability

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Message-ID: <aUuGPw0Ml+BvDL+z@hu-qianyu-lv.qualcomm.com>
Date: Tue, 23 Dec 2025 22:20:47 -0800
From: Qiang Yu <qiang.yu@....qualcomm.com>
To: Niklas Cassel <cassel@...nel.org>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Wenbin Yao <wenbin.yao@....qualcomm.com>
Subject: Re: [PATCH 2/5] PCI: dwc: Add new APIs to remove standard and
 extended Capability

On Tue, Dec 23, 2025 at 08:24:26AM +0100, Niklas Cassel wrote:
> Hello Qiang Yu,
> 
> I just saw that this patch was queued up.
> 
> dw_pcie_remove_ext_capability() basically seems to be identical to:
> dw_pcie_ep_hide_ext_capability(), only that your new function does
> not require previous cap as an argument (so it seems better).
> 
> It seems a bit silly to have two functions that do the same thing,
> perhaps you can send a patch that removes dw_pcie_ep_hide_ext_capability()
> and updates the only user of that function to use your new function?
> 
> Sorry for not seeing this earlier.
>
Hi Niklas

Thank you for the comments. I'd be happy to send a follow-up patch to 
resolve this.

- Qiang Yu
> 
> Kind regards,
> Niklas
> 
> On Sun, Nov 09, 2025 at 10:59:41PM -0800, Qiang Yu wrote:
> > On some platforms, certain PCIe Capabilities may be present in hardware
> > but are not fully implemented as defined in PCIe spec. These incomplete
> > capabilities should be hidden from the PCI framework to prevent unexpected
> > behavior.
> > 
> > Introduce two APIs to remove a specific PCIe Capability and Extended
> > Capability by updating the previous capability's next offset field to skip
> > over the unwanted capability. These APIs allow RC drivers to easily hide
> > unsupported or partially implemented capabilities from software.
> > 
> > Co-developed-by: Wenbin Yao <wenbin.yao@....qualcomm.com>
> > Signed-off-by: Wenbin Yao <wenbin.yao@....qualcomm.com>
> > Signed-off-by: Qiang Yu <qiang.yu@....qualcomm.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware.c | 53 ++++++++++++++++++++++++++++
> >  drivers/pci/controller/dwc/pcie-designware.h |  2 ++
> >  2 files changed, 55 insertions(+)