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Message-ID: <20200802201806.GA24437@nazgul.tnic>
Date: Sun, 2 Aug 2020 22:18:06 +0200
From: Borislav Petkov <bp@...en8.de>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Saheed Bolarinwa <refactormyself@...il.com>, trix@...hat.com,
Kalle Valo <kvalo@...eaurora.org>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Wolfgang Grandegger <wg@...ndegger.com>,
Marc Kleine-Budde <mkl@...gutronix.de>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Joerg Roedel <joro@...tes.org>, bjorn@...gaas.com,
skhan@...uxfoundation.org,
linux-kernel-mentees@...ts.linuxfoundation.org,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
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Subject: Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
On Sun, Aug 02, 2020 at 02:14:06PM -0500, Bjorn Helgaas wrote:
> 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?
Well, I don't think you can differentiate that case, right?
I guess this is where the driver knowledge comes into play: if the read
returns ~0, the pci_read_config* should probably return in that case
something like:
PCIBIOS_READ_MAYBE_FAILED
to denote it is all 1s and then the caller should be able to determine,
based on any of domain:bus:slot.func and whatever else the driver knows
about its hardware, whether the 1s are a valid value or an error.
Hopefully.
Or something better of which I cannot think of right now...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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