linux-kernel - Re: [PATCH 01/14] of/pci: Provide support for parsing PCI DT ranges property

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Message-ID: <50EF5798.6040405@wwwdotorg.org>
Date:	Thu, 10 Jan 2013 17:06:48 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Thierry Reding <thierry.reding@...onic-design.de>
CC:	linux-tegra@...r.kernel.org, Andrew Murray <andrew.murray@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Arnd Bergmann <arnd@...db.de>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 01/14] of/pci: Provide support for parsing PCI DT ranges
 property

On 01/09/2013 01:43 PM, Thierry Reding wrote:
> From: Andrew Murray <andrew.murray@....com>
> 
> DT bindings for PCI host bridges often use the ranges property to describe
> memory and IO ranges - this binding tends to be the same across architectures
> yet several parsing implementations exist, e.g. arch/mips/pci/pci.c,
> arch/powerpc/kernel/pci-common.c, arch/sparc/kernel/pci.c and
> arch/microblaze/pci/pci-common.c (clone of PPC). Some of these duplicate
> functionality provided by drivers/of/address.c.
> 
> This patch provides a common iterator-based parser for the ranges property, it
> is hoped this will reduce DT representation differences between architectures
> and that architectures will migrate in part to this new parser.
...

> diff --git a/drivers/of/address.c b/drivers/of/address.c

> +const __be32 *of_pci_process_ranges(struct device_node *node,

> +	while (from + np <= end) {
> +		u64 cpu_addr, size;
> +
> +		cpu_addr = of_translate_address(node, from + na);
> +		size = of_read_number(from + na + pna, ns);
> +		res->flags = bus->get_flags(from);
> +		from += np;
> +
> +		if (cpu_addr == OF_BAD_ADDR || size == 0)
> +			continue;

Hmmm. That seems to just ignore bad entries in the ranges property. Is
that really the right thing to do? At least printing a diagnostic might
be a good idea, even if the code does just soldier on in the hope
everything still works.

> +		res->name = node->full_name;
> +		res->start = cpu_addr;
> +		res->end = res->start + size - 1;
> +		res->parent = res->child = res->sibling = NULL;
> +		return from;
> +	}
> +
> +	return NULL;
> +}

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