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From: Bjorn Helgaas <helgaas@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Vignesh Raghavendra <vigneshr@ti.com>,
	linux-pci@vger.kernel.org, linux-fpga@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linux-ide@vger.kernel.org,
	linux-mtd@lists.infradead.org, linux-i2c@vger.kernel.org,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	linux-rdma@vger.kernel.org, Richard Weinberger <richard@nod.at>,
	Joerg Roedel <joro@8bytes.org>,
	linux-atm-general@lists.sourceforge.net, trix@redhat.com,
	Jakub Kicinski <kuba@kernel.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Wolfgang Grandegger <wg@grandegger.com>,
	intel-gfx@lists.freedesktop.org, linux-gpio@vger.kernel.org,
	Marc Kleine-Budde <mkl@pengutronix.de>,
	skhan@linuxfoundation.org, bjorn@helgaas.com,
	Kalle Valo <kvalo@codeaurora.org>,
	linux-edac@vger.kernel.org, linux-hwmon@vger.kernel.org,
	Saheed Bolarinwa <refactormyself@gmail.com>,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, linux-crypto@vger.kernel.org,
	netdev@vger.kernel.org, dmaengine@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
Date: Sun, 2 Aug 2020 14:14:06 -0500
Message-ID: <20200802191406.GA248232@bjorn-Precision-5520> (raw)
In-Reply-To: <20200802184648.GA23190@nazgul.tnic>

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
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Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 11:24 Saheed O. Bolarinwa
2020-08-01 11:24 ` [RFC PATCH 09/17] drm/i915/vga: " Saheed O. Bolarinwa
2020-08-01 12:56 ` [RFC PATCH 00/17] " Borislav Petkov
2020-08-02 14:53   ` Tom Rix
2020-08-02 17:28   ` Saheed Bolarinwa
2020-08-02 18:46     ` Borislav Petkov
2020-08-02 19:14       ` Bjorn Helgaas [this message]
2020-08-02 20:18         ` Borislav Petkov

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