[PATCH 09/17] ARM: add atag32_to_cpu() function

[Jean-Christophe PLAGNIOL-VILLARD]

On 19:15 Mon 11 Feb     , Ben Dooks wrote:
> On 09/02/13 12:03, Russell King - ARM Linux wrote:
> >On Fri, Feb 08, 2013 at 11:17:39PM +0000, Ben Dooks wrote:
> >>Add atag32_to_cpu() function to allow code manipulating ATAGs to deal
> >>with the case where the boot-loader was in little-endian and Linux is
> >>running big-endian.
> >...
> >>+#ifdef CONFIG_CPU_BE8_BOOT_LE
> >>+#define atag32_to_cpu(x)	le32_to_cpu(x)
> >>+#else
> >>+#define atag32_to_cpu(x)	x
> >>+#endif
> >
> >Actually, with a LE kernel, le32_to_cpu() ends up being a no-op too.  So
> >I'm wondering if we should do this a different way...
> >
> >Also, this will cause sparse to complain - le32_to_cpu() takes a le32
> >type not a u32 type.
> 
> Yes, you're right on that.
> 
> >This brings up a whole load of difficulties though: what format are the
> >ATAGs on older BE hardware - I bet it's CPU-endian format there.  So,
> >I'm wondering if we should do this:
> 
> It isn't defined, and I have failed to find any information on
> it online. I have no idea if the IXP devices ran their boot-loader
> in big-endian or little-endian format?
> 
> Input welcome from anyone who can remember.
I run the ixp in be

and pass the atag in be

Best Regards,
J.
> 
> >1. define all tags using a new __atagXX, etc types.
> >2. always use atagXX_to_cpu() to read these.
> >3. Implement:
> >
> >#if defined(CONFIG_ATAG_LE)
> >typedef __le32 __atag32;
> >...
> >#define atag32_to_cpu(x) le32_to_cpu(x)
> >...
> >#elif defined(CONFIG_ATAG_BE)
> >typedef __be32 __atag32;
> >...
> >#define atag32_to_cpu(x) be32_to_cpu(x)
> >...
> >#elif defined(CONFIG_ATAG_NE)
> >typedef __u32 __atag32;
> >...
> >#define atag32_to_cpu(x) x
> >...
> >#endif
> >
> >and select the appropriate definition.  Obviously, this is a fundamental
> >configuration just like the overall BE/LE configuration of the kernel.
> 
> Ok, should I sort out doing that for the next round of patches?
> 
> Should the ATAG_xx configurations go into arch/arm/Kconfig or
> is there somewhere better for them to go?
> 
> -- 
> Ben Dooks				http://www.codethink.co.uk/
> Senior Engineer				Codethink - Providing Genius
> 
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