linux-kernel - Re: sb_edac 32-bit compile fail due to 64-bit divide

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Message-ID: <4EB2A5FF.1040808@redhat.com>
Date:	Thu, 03 Nov 2011 12:32:31 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Josh Boyer <jwboyer@...hat.com>
CC:	linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: sb_edac 32-bit compile fail due to 64-bit divide

Em 03-11-2011 12:07, Josh Boyer escreveu:
> Hi,
> 
> It seems the newly added EDAC driver for SandyBridge won't build on
> 32-bit x86 because of a 64-bit divide somewhere:
> 
> 	drivers/edac/sb_edac.c: In function 'get_memory_error_data':
> 	drivers/edac/sb_edac.c:861:2: warning: left shift count >= width of type
> 	[enabled by default]
> 	<snip>
> 	ERROR: "__udivdi3" [drivers/edac/sb_edac.ko] undefined!
> 	make[1]: *** [__modpost] Error 1
> 	make: *** [modules] Error 2
> 
> You can find the full build log here:
> 
> http://koji.fedoraproject.org/koji/getfile?taskID=3482579&name=build.log
> 
> Before I go digging into where this is done and what to do about it, I
> do want to confirm that it is supposed to work on a 32-bit kernel,
> correct?

Thanks for pointing it!

Well, I didn't test it on a 32-bit kernel. It should work through.

It is probably due to those debug lines:
	debugf0("CH#%d RIR#%d INTL#%d, offset %Lu.%03Lu GB (0x%016Lx), tgt: %d, reg=0x%08x\n",
        	i, j, k,
                tmp_mb / 1000, tmp_mb % 1000,
                ((u64)tmp_mb) << 20L,
                (u32)RIR_RNK_TGT(reg),
                reg);
(same kind of calculus is recurrent at the driver)

Maybe the easiest way would be to write a function that would call do_div() internally,
and output a string with something similar to:

	sprintf(msg, "%Lu.%03Lu GB", tmp_mb / 1000, tmp_mb % 1000);

Of course, an interim fix would be to make it depend on CONFIG_64BIT or CONFIG_X86_64.

Regards,
Mauro
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