linux-kernel - Re: [PATCH 1/2] regmap: debugfs: remove bogus check

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Message-ID: <87d1wzg5gl.fsf@rasmusvillemoes.dk>
Date:	Wed, 30 Sep 2015 19:52:26 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Mark Brown <broonie@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] regmap: debugfs: remove bogus check

On Wed, Sep 30 2015, Mark Brown <broonie@...nel.org> wrote:

> On Wed, Sep 30, 2015 at 09:27:38AM +0200, Rasmus Villemoes wrote:
>
>> I agree, but only on the word 'great'. There is value in removing such
>> bogosities (or rather, their presence provides negative value). It makes
>> the code harder to read ("why is this instance checked, but not any of
>> the other snprintfs?"); people may think that it's trying to check for
>> truncation, but it does no such thing; and it contributes a few
>> worthless bytes to .text (and the source).
>
> The solution to partial error checking isn't always to remove the error
> checking!

Since this particular piece of code is not, in fact, doing any kind of error
checking, I fail to see how that argument is relevant.

Or, more constructively: Would you please explain exactly what error
checking you think this should/could be doing? Truncation? Invalid
format string? Cosmic-ray-detected?

>> If you're worried about map->dev->driver->name actually ever being > 2G,
>> returning some almost totally random negative number isn't really
>> helpful (the function is supposed to return a -errno). And what makes
>> you think that in some hypothetical universe where the kernel's snprintf
>> explicit returns a negative value that it wouldn't just return -1 (aka
>> -EPERM)?
>
> This is going back to the discussion about having to learn the specific
> snprinf() implementation one is dealing with.

You better know what values it might return under which circumstances if
you're going to forward those as error codes to your caller.

Rasmus
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