linux-kernel - Re: [PATCH v12 0/6] Refactor capability search into common macros

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Message-ID: <60860792-ef02-4c10-b313-b3f34bab0a8b@163.com>
Date: Mon, 26 May 2025 22:53:15 +0800
From: Hans Zhang <18255117159@....com>
To: lpieralisi@...nel.org, bhelgaas@...gle.com,
 manivannan.sadhasivam@...aro.org, ilpo.jarvinen@...ux.intel.com, kw@...ux.com
Cc: cassel@...nel.org, robh@...nel.org, jingoohan1@...il.com,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 0/6] Refactor capability search into common macros


Dear Ilpo,

May I ask if you have time to review the patches of this series? If 
there are any problems, I can continue to improve. If you think there is 
no problem, could you review it and add review tags?


Best regards,
Hans

On 2025/5/15 00:12, Hans Zhang wrote:
> Dear Maintainers,
> 
> This patch series addresses long-standing code duplication in PCI
> capability discovery logic across the PCI core and controller drivers.
> The existing implementation ties capability search to fully initialized
> PCI device structures, limiting its usability during early controller
> initialization phases where device/bus structures may not yet be
> available.
> 
> The primary goal is to decouple capability discovery from PCI device
> dependencies by introducing a unified framework using config space
> accessor-based macros. This enables:
> 
> 1. Early Capability Discovery: Host controllers (e.g., Cadence, DWC)
> can now perform capability searches during pre-initialization stages
> using their native config accessors.
> 
> 2. Code Consolidation: Common logic for standard and extended capability
> searches is refactored into shared macros (`PCI_FIND_NEXT_CAP_TTL` and
> `PCI_FIND_NEXT_EXT_CAPABILITY`), eliminating redundant implementations.
> 
> 3. Safety and Maintainability: TTL checks are centralized within the
> macros to prevent infinite loops, while hardcoded offsets in drivers
> are replaced with dynamic discovery, reducing fragility.
> 
> Key improvements include:
> - Driver Conversions: DesignWare and Cadence drivers are migrated to
>    use the new macros, removing device-specific assumptions and ensuring
>    consistent error handling.
> 
> - Enhanced Readability: Magic numbers are replaced with symbolic
>    constants, and config space accessors are standardized for clarity.
> 
> - Backward Compatibility: Existing PCI core behavior remains unchanged.
> 
> ---
> Changes since v11:
> - Resolved some compilation warning.
> - Add some include.
> - Add the *** BLURB HERE *** description(Corrected by Mani and Krzysztof).
> 
> Changes since v10:
> - The patch [v10 2/6] remove #include <uapi/linux/pci_regs.h> and add macro definition comments.
> - The patch [v10 3/6] remove #include <uapi/linux/pci_regs.h> and commit message were modified.
> - The other patches have not been modified.
> 
> Changes since v9:
> - Resolved [v9 4/6] compilation error.
>    The latest 6.15 rc1 merge __dw_pcie_find_vsec_capability, which uses
>    dw_pcie_find_next_ext_capability.
> - The other patches have not been modified.
> 
> Changes since v8:
> - Split patch.
> - The patch commit message were modified.
> - Other patches(4/6, 5/6, 6/6) are unchanged.
> 
> Changes since v7:
> - Patch 2/5 and 3/5 compilation error resolved.
> - Other patches are unchanged.
> 
> Changes since v6:
> - Refactor capability search into common macros.
> - Delete pci-host-helpers.c and MAINTAINERS.
> 
> Changes since v5:
> - If you put the helpers in drivers/pci/pci.c, they unnecessarily enlarge
>    the kernel's .text section even if it's known already at compile time
>    that they're never going to be used (e.g. on x86).
> - Move the API for find capabilitys to a new file called
>    pci-host-helpers.c.
> - Add new patch for MAINTAINERS.
> 
> Changes since v4:
> - Resolved [v4 1/4] compilation warning.
> - The patch subject and commit message were modified.
> 
> Changes since v3:
> - Resolved [v3 1/4] compilation error.
> - Other patches are not modified.
> 
> Changes since v2:
> - Add and split into a series of patches.
> ---
> 
> Hans Zhang (6):
>    PCI: Introduce generic bus config read helper function
>    PCI: Clean up __pci_find_next_cap_ttl() readability
>    PCI: Refactor capability search into common macros
>    PCI: dwc: Use common PCI host bridge APIs for finding the capabilities
>    PCI: cadence: Use common PCI host bridge APIs for finding the
>      capabilities
>    PCI: cadence: Use cdns_pcie_find_*capability to avoid hardcode.
> 
>   drivers/pci/access.c                          | 17 ++++
>   .../pci/controller/cadence/pcie-cadence-ep.c  | 40 +++++----
>   drivers/pci/controller/cadence/pcie-cadence.c | 28 ++++++
>   drivers/pci/controller/cadence/pcie-cadence.h | 18 ++--
>   drivers/pci/controller/dwc/pcie-designware.c  | 81 +++--------------
>   drivers/pci/pci.c                             | 68 ++------------
>   drivers/pci/pci.h                             | 88 +++++++++++++++++++
>   include/uapi/linux/pci_regs.h                 |  2 +
>   8 files changed, 194 insertions(+), 148 deletions(-)
> 
> 
> base-commit: 82f2b0b97b36ee3fcddf0f0780a9a0825d52fec3