linux-kernel - Re: [PATCH v2 2/7] PCI: ACPI: PM: Do not use pci_platform_pm

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Message-ID: <CAJZ5v0jSOpBbt8C5ema1t7h8Fb49F7DSyrUfht5xUXibVBU2Qw@mail.gmail.com>
Date:   Wed, 29 Sep 2021 21:13:07 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH v2 2/7] PCI: ACPI: PM: Do not use pci_platform_pm_ops for ACPI

On Wed, Sep 29, 2021 at 9:08 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Mon, Sep 20, 2021 at 09:17:08PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Using struct pci_platform_pm_ops for ACPI adds unnecessary
> > indirection to the interactions between the PCI core and ACPI PM,
> > which is also subject to retpolines.
> >
> > Moreover, it is not particularly clear from the current code that,
> > as far as PCI PM is concerned, "platform" really means just ACPI
> > except for the special casess when Intel MID PCI PM is used or when
> > ACPI support is disabled (through the kernel config or command line,
> > or because there are no usable ACPI tables on the system).
> >
> > To address the above, rework the PCI PM code to invoke ACPI PM
> > functions directly as needed and drop the acpi_pci_platform_pm
> > object that is not necessary any more.
> >
> > Accordingly, update some of the ACPI PM functions in question to do
> > extra checks in case the ACPI support is disabled (which previously
> > was taken care of by avoiding to set the pci_platform_ops pointer
> > in those cases).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> This patch as commit 9896a58cdd59 ("PCI: ACPI: PM: Do not use
> pci_platform_pm_ops for ACPI") in -next causes the following build error
> when compiling x86_64 allmodconfig with clang:
>
> drivers/pci/pci-acpi.c:1125:7: error: variable 'adev' is uninitialized when used here [-Werror,-Wuninitialized]
>         if (!adev || !acpi_device_power_manageable(adev))
>              ^~~~
> drivers/pci/pci-acpi.c:1110:26: note: initialize the variable 'adev' to silence this warning
>         struct acpi_device *adev;
>                                 ^
>                                  = NULL
> 1 error generated.
>
> Should the adev assignment be moved up

Yes, thanks!

I'll fix it up in the tree.