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Date:   Sun, 2 Aug 2020 14:14:06 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Saheed Bolarinwa <refactormyself@gmail.com>, trix@redhat.com,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
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        Wolfgang Grandegger <wg@grandegger.com>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
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Subject: Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
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On Sun, Aug 02, 2020 at 08:46:48PM +0200, Borislav Petkov wrote:
> On Sun, Aug 02, 2020 at 07:28:00PM +0200, Saheed Bolarinwa wrote:
> > Because the value ~0 has a meaning to some drivers and only
> 
> No, ~0 means that the PCI read failed. For *every* PCI device I know.

Wait, I'm not convinced yet.  I know that if a PCI read fails, you
normally get ~0 data because the host bridge fabricates it to complete
the CPU load.

But what guarantees that a PCI config register cannot contain ~0?
If there's something about that in the spec I'd love to know where it
is because it would simplify a lot of things.

I don't think we should merge any of these patches as-is.  If we *do*
want to go this direction, we at least need some kind of macro or
function that tests for ~0 so we have a clue about what's happening
and can grep for it.

Bjorn