linux-kernel - Re: [PATCH 1/5] mtd: st_spi_fsm: Remove useless consts from function arguments

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Date:	Thu, 20 Mar 2014 05:41:00 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	kernel@...inux.com,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Angus CLARK <angus.clark@...com>
Subject: Re: [PATCH 1/5] mtd: st_spi_fsm: Remove useless consts from function arguments

On Thu, Mar 20, 2014 at 5:13 AM, Joe Perches <joe@...ches.com> wrote:
> On Thu, 2014-03-20 at 12:03 +0000, Lee Jones wrote:
>> > Good catch. That wasn't my intention.
>> > > Why?
>> An oversight.
>
> That's still not an explanation.
>
> Why, unless cast away by the code itself, is
> const removal a good thing?

It's not so much removal as it is review of the initial driver merge.
I'd contend that const was applied somewhat thoughtlessly originally,
and it didn't really serve a good purpose.

> It does serve as an indication to a reader what
> the code does with the argument.
>
> About the only reason I can think of arguing in
> favor of removal is inconsistent application of
> const within the module.

That's one good reason. And not only consistency within the modules,
but consistency within the subsystem (and the kernel at large,
really). There's rarely a case of a const function parameter. And I'm
sure there are numerous function parameters which could potentially be
marked 'const'.

I also don't think that a function parameter is the right place to
mark const like this. Function arguments are always pass-by-value, so
this 'const' tells users (callers) nothing useful. It only provides
useless constraints on what the function can do with its copy of the
parameter.

Brian
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