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Subject: Re: [RFC/PATCH] Documentation of kernel messages
From: holzheu <holzheu@linux.vnet.ibm.com>
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To: Jan Kara <jack@suse.cz>
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Date: Thu, 14 Jun 2007 12:38:53 +0200
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On Thu, 2007-06-14 at 11:41 +0200, Jan Kara wrote:
>   <snip>
> 
> > Your proposal is similar to one I made to some Japanese developers
> > earlier this year.  I was more modest, proposing that we
> > 
> > - add an enhanced printk
> > 
> > 	xxprintk(msgid, KERN_ERR "some text %d\n", some_number);
>   Maybe a stupid idea but why do we want to assign these numbers by hand?
> I can imagine it could introduce collisions when merging tons of patches
> with new messages... Wouldn't it be better to compute say, 8-byte hash
> from the message and use it as it's identifier? We could do this
> automagically at compile time.

Of course automatically generated message numbers would be great and
something like:

hub.4a5bcd77: Detected some problem.

looks acceptable for me.

We could generate the hash using the format string of the printk. Since
we specify the format string also in KMSG_DOC, the hash for the
KMSG_DOC and the printk should match and we have the required link
between printk and description.

So technically that's probably doable.

Problems are:

* hashes are not unique
* We need an additional preprocessor step
* The might be people, who find 8 character hash values ugly in printks

The big advantage is, that we do not need to maintain message numbers.

> I know it also has it's problems - you
> fix a spelling and the message gets a different id and you have to
> update translation/documentation catalogue but maybe that could be
> solved too...

Since in our approach the message catalog is created automatically for
exactly one kernel and the message catalog belongs therefore to exactly
one kernel, I think the problem of changing error numbers is not too
big.

Michael

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