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

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Message-Id: <200610201023.12796.arnd@arndb.de>
Date:	Fri, 20 Oct 2006 10:23:10 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	cbe-oss-dev@...abs.org, linux-kernel@...r.kernel.org
Cc:	Dwayne Grant McConnell <decimal@...ibm.com>,
	linuxppc-dev@...abs.org
Subject: Re: Correct way to format spufs file output.

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.

	Arnd <><

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