From: Rusty Russell <rusty@rustcorp.com.au>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Minfei Huang <mhuang@redhat.com>, rob.jones@codethink.co.uk,
        amhyung@kernel.org, linux-kernel@vger.kernel.org,
        Minfei Huang <mnfhuang@gmail.com>
Subject: Re: [PATCH 1/2] Define find_symbol_in_section_t as function type to simplify the code
In-Reply-To: <20150715133126.c13ff1e75bf36eb0a85dcb3f@linux-foundation.org>
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Date: Thu, 16 Jul 2015 20:59:47 +0930
Message-ID: <87mvywmjbo.fsf@rustcorp.com.au>
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Andrew Morton <akpm@linux-foundation.org> writes:
> On Wed, 15 Jul 2015 07:22:32 +0930 Rusty Russell <rusty@rustcorp.com.au> wrote:
>> It's shorter, but it's less clear.  typedefs on functions are not very
>> useful:
>> 1) They require readers to look in two places to see how to use the
>>    function (ie each_symbol_section).
>> 2) They can't use the typedef to declare their function, since that
>>    doesn't work in C.
>> 
>> If the function were being used many times, it makes sense.  But
>> it's only used twice, once static inside module.c.
>> 
>
> Using a foo_t typedef for a function callback is a common pattern. 
> It's (almost) the only approved use of typedefs.  The usage is
> widespread enough that when one sees a foo_t type, one says "ahah,
> that's a function pointer".

I always thought of a type which can map to varying types under
different arch/configs as the typical typedef.

> Sorry, but I don't think "Rusty doesn't like it" is a good reason for
> the module code to be different.

But "Rusty has to maintain it" is a pretty strong counter argument,
IMHO.

> All of us dislike some aspects of
> kernel coding practices, but we go along because consistency is more
> important.

Consistency is important when it makes things more readable, sure.

I don't think any kernel devs are going to get confused seeing a
function pointer, and I think this patch makes the code slightly
less readable.

Enough not to apply the patch, but not enough waste more time on it.

Cheers,
Rusty.
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