linux-kernel - Re: [PATCH] debugfs: New debugfs interface for creation of files, directory and symlinks

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Date:	Wed, 2 May 2012 15:44:38 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Sasikanth babu <sasikanth.v19@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] debugfs: New debugfs interface for creation of files,
 directory and symlinks

On Wed, 2 May 2012 15:36:03 -0700
Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:

> > 
> > The API is stupid and wrong, actually.  There is no *advantage* to
> > having done it this way - none at all.
> 
> Yes there is, it makes the caller logic trivial, which was the main goal
> here in getting people to use it over creating new proc files all the
> time for no good reason.
> 
> No one cares about the return value when you create a proc file, either
> it succeeds or not, and you handle things from there, you never change
> the name to try it again.
> 
> Same thing with debugfs, you only care if it works or not, and really,
> you don't even care if it works, as the api lets you continue on if it
> didn't just fine.
> 
> These are debugging files, with no set rules on what they contain.  Yes,
> people have grown to get used to them over the years, but the namespace
> in which they work has worked out for itself, and I have yet to ever
> hear of any two people wanting to create the same file/directory
> anywhere, and have anything fail.
> 
> Or am I missing some subsystem that is having problems like this with
> debugfs?

grr, you appear to have ignored everything I wrote.  Here it is again:

> > That's the whole reason we have errnos: to report on what went wrong,
> > so operators can understand *why* it failed and so that programmers can
> > diagnose and fix bugs.

and

> > If well-written code checks the return value (as it should) and then
> > propagates an error code back to its caller (as it should), the stupid
> > debugfs interface forces that caller to invent an errno from thin air.
> > And if that guessed errno is wrong, it is actively misleading!

I would add that an interface which encourages callers to silently
ignore programming and configuration errors is not a good one.

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