linux-kernel - Re: [RFC PATCH 1/3] PCI: Add standard PCI Config Address macros

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Message-ID: <20220913211143.GA624473@bhelgaas>
Date:   Tue, 13 Sep 2022 16:11:43 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Sergio Paracuellos <sergio.paracuellos@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] PCI: Add standard PCI Config Address macros

On Sun, Sep 11, 2022 at 01:20:22PM +0200, Pali Rohár wrote:
> Lot of PCI and PCIe controllers are using standard Config Address for PCI
> Configuration Mechanism #1 (as defined inPCI Local Bus Specification) or
> its extended version.
> 
> So introduce new macros PCI_CONF1_ADDRESS() and PCI_CONF1_EXT_ADDRESS() in
> new include file linux/pci-conf1.h which can be suitable for PCI and PCIe
> controllers which uses this type of access to PCI config space.
> 
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
>  include/linux/pci-conf1.h | 51 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 include/linux/pci-conf1.h

This seems like a nice addition, but it would be nice if we could
encapsulate it in drivers/pci.

I know it's parallel to the existing include/linux/pci-ecam.h.  I wish
we could encapsulate *that* in drivers/pci, too.  For pci-ecam.h, I
think the only things that prevent that are drivers/acpi/pci_mcfg.c,
loongarch, and a few arm64 things.

pci_mcfg.c arguably would make more sense in drivers/pci; it uses
acpi_table_parse(), but no other ACPI services.

The arm64 code that uses pci-ecam.h is really generic code that would
not be in arch/arm64 except for the fact that x86 has really ugly
legacy x86-specific mmconfig code.

I guess that's a long-winded way of saying that I think maybe we could
put this in drivers/pci/pci.h even though the parallel ECAM stuff is
in include/linux/pci-ecam.h.

Bjorn