Re: [PATCH v15 0/6] Refactor capability search into common macros

[Hans Zhang]

On 2025/8/14 16:32, Niklas Schnelle wrote:
> On Wed, 2025-08-13 at 22:45 +0800, 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` and
> > `PCI_FIND_NEXT_EXT_CAP`), 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.
> >
> > ---
> > Dear Niklas and Gerd,
> >
> > Can you test this series of patches on the s390?
> >
> > Thank you very much.
>
> Hi Hans, I gave this series a try on top of v6.17-rc1 on s390
> and a bunch of PCI devices including the mlx5 cards that Gerd we
> originally saw issues with. All looks well now. So feel free to
> add as appropriate:
>
> Tested-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>

Hi Niklas,

Thank you very much for your test. Let's see what others think.

Best regards,
Hans