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From: Borislav Petkov <bp@alien8.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Saheed Bolarinwa <refactormyself@gmail.com>,
	trix@redhat.com, Kalle Valo <kvalo@codeaurora.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Wolfgang Grandegger <wg@grandegger.com>,
	Marc Kleine-Budde <mkl@pengutronix.de>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Joerg Roedel <joro@8bytes.org>,
	bjorn@helgaas.com, skhan@linuxfoundation.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
	linux-mtd@lists.infradead.org, iommu@lists.linux-foundation.org,
	linux-rdma@vger.kernel.org, linux-ide@vger.kernel.org,
	linux-i2c@vger.kernel.org, linux-hwmon@vger.kernel.org,
	dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	linux-gpio@vger.kernel.org, linux-fpga@vger.kernel.org,
	linux-edac@vger.kernel.org, dmaengine@vger.kernel.org,
	linux-crypto@vger.kernel.org,
	linux-atm-general@lists.sourceforge.net
Subject: Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
Date: Sun, 2 Aug 2020 22:18:06 +0200
Message-ID: <20200802201806.GA24437@nazgul.tnic> (raw)
In-Reply-To: <20200802191406.GA248232@bjorn-Precision-5520>

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

  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 11:24 Saheed O. Bolarinwa
2020-08-01 11:24 ` [RFC PATCH 04/17] hwrng: " 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
2020-08-02 20:18         ` Borislav Petkov [this message]
2020-08-03  6:56         ` Christoph Hellwig

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