From: Borislav Petkov <bp@alien8.de>
To: Saheed Bolarinwa <refactormyself@gmail.com>
Cc: trix@redhat.com, helgaas@kernel.org,
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 20:46:48 +0200 [thread overview]
Message-ID: <20200802184648.GA23190@nazgul.tnic> (raw)
In-Reply-To: <b720aa44-895a-203b-e220-ecdb3acd9278@gmail.com>
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.
Here's me reading from 0xf0 offset of my hostbridge:
# setpci -s 00:00.0 0xf0.l
01000000
That device doesn't have extended config space, so the last valid byte
is 0xff. Let's read beyond that:
# setpci -s 00:00.0 0x100.l
ffffffff
> Again, only the drivers can determine if ~0 is a valid value. This
> information is not available inside pci_config_read*().
Of course it is.
*every* change you've done in 6/17 - this is the only patch I have
received - checks for == ~0. So that check can just as well be moved
inside pci_config_read_*().
Here's how one could do it:
#define PCI_OP_READ(size, type, len) \
int noinline pci_bus_read_config_##size \
(struct pci_bus *bus, unsigned int devfn, int pos, type *value) \
{ \
int res; \
unsigned long flags; \
u32 data = 0; \
if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \
pci_lock_config(flags); \
res = bus->ops->read(bus, devfn, pos, len, &data); \
/* Check we actually read something which is not all 1s.*/
if (data == ~0)
return PCIBIOS_READ_FAILED;
*value = (type)data; \
pci_unlock_config(flags); \
return res; \
}
Also, I'd prefer a function to *not* return void but return either
an error or success. In the success case, the @value argument can be
consumed by the caller and otherwise not.
In any case, that change is a step in the wrong direction and I don't
like it, sorry.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-08-02 18:47 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-01 11:24 [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value Saheed O. Bolarinwa
2020-08-01 11:24 ` [RFC PATCH 06/17] edac: " 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 [this message]
2020-08-02 19:14 ` Bjorn Helgaas
2020-08-02 20:18 ` Borislav Petkov
2020-08-03 6:56 ` Christoph Hellwig
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