From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Grzegorz Jaszczyk <jaz@semihalf.com>,
lorenzo.pieralisi@arm.com, bhelgaas@google.com,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
mw@semihalf.com
Subject: Re: [PATCH] PCI: aardvark: fix big endian support
Date: Tue, 16 Jul 2019 09:56:31 +0100 [thread overview]
Message-ID: <20190716085631.yst3kcrxtkh23xtq@shell.armlinux.org.uk> (raw)
In-Reply-To: <20190716083204.375afc1e@windsurf>
On Tue, Jul 16, 2019 at 08:32:04AM +0200, Thomas Petazzoni wrote:
> Hello,
>
> On Mon, 15 Jul 2019 16:10:16 +0100
> Russell King - ARM Linux admin <linux@armlinux.org.uk> wrote:
>
> > > Also, the advk_pci_bridge_emul_pcie_conf_read() and
> > > advk_pci_bridge_emul_pcie_conf_write() return values that are in the
> > > CPU endianness.
> > >
> > > Am I missing something ?
> >
> > Getting the types correct and then using Sparse to validate the code
> > will help to identify issues exactly like this.
>
> Yes, I absolutely agree with your recommendation on the other thread.
>
> In fact, I am wondering if it really makes sense to store the "fake"
> config space in LE, since anyway the read/write accessors should return
> values in the CPU endianness.
Consider:
u16 vendor;
u16 device;
and how they are laid out in LE and BE. Then consider what happens
when you read "vendor" using a u32 accessor. This is where the
problem lies.
Using host endian means you'd have to read the members using an
appropriately sized host access (in other words, not using a dword
accessor) to end up with the correct result - but we don't want a
large switch() statement here...
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2019-07-16 8:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 14:15 [PATCH] PCI: aardvark: fix big endian support Grzegorz Jaszczyk
2019-07-15 15:08 ` Thomas Petazzoni
2019-07-15 15:10 ` Russell King - ARM Linux admin
2019-07-16 6:32 ` Thomas Petazzoni
2019-07-16 8:56 ` Russell King - ARM Linux admin [this message]
2019-07-16 8:31 ` Grzegorz Jaszczyk
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