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Subject: Re: PCI: mvebu: return NULL instead of ERR_PTR(ret)
From: Joe Perches <joe@perches.com>
To: Jingoo Han <jg1.han@samsung.com>
Cc: 'Christopher Li' <sparse@chrisli.org>,
	linux-sparse@vger.kernel.org,
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	linux-pci@vger.kernel.org,
	'Ezequiel Garcia' <ezequiel.garcia@free-electrons.com>,
	linux-arm-kernel@lists.infradead.org,
	'Axel Lin' <axel.lin@ingics.com>,
	'Julia Lawall' <julia.lawall@lip6.fr>
Date: Tue, 26 Nov 2013 18:26:36 -0800
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On Wed, 2013-11-27 at 10:59 +0900, Jingoo Han wrote:
[]
> ./drivers/pci/host/pci-mvebu.c
> static void __iomem *mvebu_pcie_map_registers(struct platform_device *pdev,
> 		struct device_node *np, struct mvebu_pcie_port *port)
> {
> 	.....
> 
> 	ret = of_address_to_resource(np, 0, &regs);
> 	if (ret)
> -		return ERR_PTR(ret);
> +		return (void __iomem *)ERR_PTR(ret);
> 
> However, other engineers said that "(void __iomem *)ERR_PTR(ret)"
> is not a general pattern. I cannot find the proper method to resolve
> this sparse warning.
> 
> In this case, how can I resolve this sparse warning?

I think there's no problem using the cast.  It's not a
pattern because it's not been required before as function
returns have not previously been declared __iomem.

Or, perhaps the arm|hexagon specific #define below could
be made generic so it could be used.

arch/arm/include/asm/io.h:#define IOMEM(x)	((void __force __iomem *)(x))

	return IOMEM(ERR_PTR(ret));

There aren't any current uses of return IOMEM(foo) either
though so the direct cast is probably more appropriate.