linux-kernel - Re: Correct way to format spufs file output.

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Date:	Fri, 20 Oct 2006 08:54:37 -0500 (Central Daylight Time)
From:	Dwayne Grant McConnell <decimal@...ibm.com>
To:	Arnd Bergmann <arnd@...db.de>
cc:	cbe-oss-dev@...abs.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: Re: Correct way to format spufs file output.

On Fri, 20 Oct 2006, Arnd Bergmann wrote:

> On Thursday 19 October 2006 05:30, Dwayne Grant McConnell wrote:
> > In a recent submission I added the lslr file and used "%llx" for the 
> > format string. You mentioned that it should probably be "0x%llx" so it 
> > would be clearly parsed as hex so I changed it in the next submission. But 
> > I noticed that there seems to be some inconsistent usage of 0x as follows:
> 
> Thanks for bringing this up, I guess I screwed up in some way here, so
> we should fix it up one way or another:
> 
> > signal1_type (%llu)
> > signal2_type (%llu)
> 
> These are fine, they can only ever be 1 or 0.
> 
> > npc (%llx)
> 
> I think we used to access this in _very_ old versions of libspe,
> before we move to a syscall based interface.
> 
> > decr (%llx)
> > decr_status (%llx)
> > spu_tag_mask (%llx)
> > event_mask (%llx)
> > event_status (%llx)
> > srr0 (%llx)
> 
> These are used exclusively for debugging purposes, and no publically
> available version of gdb accesses them, so I guess we can still change
> them, although it's not nice.
> 
> > phys_id (0x%llx)
> 
> This one is used in some forks of libspe, we should not change it.
> 
> > object_id (0x%llx)
> 
> This is used in libspe, gdb and oprofile, but only in fairly recent
> versions.
> 
> > lslr (0x%llx)
> 
> As this is introduced by your own patch, there is no precedent for
> it yet.
> 
> Current kernels now also have 'cntl' (0x%08lx), which was introduced
> in 2.6.19 and is so far unused. I guess we should change that one
> to be consistant with the others as well.
> 
> > Should all the %llx be changed to 0x%llx or should the 0x be dropped from 
> > those that have it or is the inconsistency acceptable?
> 
> I'd rather have it consistant. Moreover, I guess the "%llx" format is
> actually harmful, because that means you can not use the same format
> for read and write. The simple_attr_write function currently uses
> the simple_strtol helper to interpret the value written to it, and that
> requires the input to be wither decimal, or hexadecimal with a preceding
> 0x. I'd suggest we change all files to take a 0x%llx format on output.

I think %0xllx is the way to go. I would even advocate changing 
signal1_type and signal2_type unless it is actually too dangerous. Is 
there even a case where changing from %llu to %0xllx would break things? 
Perhaps with the combination of a old library with a new kernel?

-- 
Dwayne Grant McConnell <decimal@...ibm.com>
Lotus Notes Mail: Dwayne McConnell [Mail]/Austin/IBM@...US
Lotus Notes Calendar: Dwayne McConnell [Calendar]/Austin/IBM@...US

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