Re: [PATCH 0/4] PCI: Add support and tests for FIXUP quirks in modules

[Brian Norris <briannorris@chromium.org>]

Hi Christoph,

On Mon, Sep 15, 2025 at 06:48:22AM -0700, Christoph Hellwig wrote:
> On Fri, Sep 12, 2025 at 03:59:31PM -0700, Brian Norris wrote:
> > This series primarily adds support for DECLARE_PCI_FIXUP_*() in modules.
> > There are a few drivers that already use this, and so they are
> > presumably broken when built as modules.
> 
> That's a reall bad idea, because it allows random code to insert quirks
> not even bound to the hardware they support.

I see fixups in controller drivers here:

drivers/pci/controller/dwc/pci-imx6.c
drivers/pci/controller/dwc/pci-keystone.c
drivers/pci/controller/dwc/pcie-qcom.c
drivers/pci/controller/pci-loongson.c
drivers/pci/controller/pci-tegra.c
drivers/pci/controller/pcie-iproc-bcma.c
drivers/pci/controller/pcie-iproc.c

Are any of those somehow wrong?

And if they are not wrong, then is this a good reason to disallow making
these drivers modular? (Yes, few of them are currently modular; but I
don't see why that *must* be the case.)

I agree, as with many kernel features, there are plenty of ways to use
them incorrectly. But I'm just trying to patch over one rough edge about
how to use them incorrectly, and I don't really see why it's such a bad
idea.

> So no, modules should not allow quirks, but the kernel should probably
> be nice enough to fail compilation when someone is attemping that
> instead of silently ignoring the quirks.

Sure, if consensus says we should not support this, I'd definitely like
to make this failure mode more obvious -- likely a build error.

Thanks for your thoughts,
Brian