linux-kernel - Re: Converting struct timer_list callback argument to struct timer

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Date:   Sun, 3 Sep 2017 00:37:57 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Converting struct timer_list callback argument to struct
 timer_list *

On Fri, Sep 01, 2017 at 09:24:22AM -0700, Kees Cook wrote:
> #define list_entry(ptr, type, member) container_of(ptr, type, member)
> #define rb_entry(ptr, type, member) container_of(ptr, type, member)
> 
> The use of a "timer_entry()" at the start of callbacks repeats the
> struct name, which I find irritating (and it usually results in split
> lines). For example:
> 
> #define timer_entry(ptr, type, member) container_of(ptr, type, member)
> 
> -static void snd_card_asihpi_timer_function(unsigned long data)
> +static void snd_card_asihpi_timer_function(struct timer_list *t)
>  {
> -       struct snd_card_asihpi_pcm *dpcm = (struct snd_card_asihpi_pcm *)data;
> +       struct snd_card_asihpi_pcm *dpcm =
> +                                timer_entry(t, struct
> snd_card_asihpi_pcm, timer);
> 
> I prefer to tie this directly to the variable, so how about renaming
> TIMER_CONTAINER to timer_of():

The TIMER_CONTAINER semantics are more useful indeed, and I which
we'd have a general purpose variant of that.  But I was complaining
about the name anyway.  timer_of sounds ok, but timer_entry still sounds
a bit more descriptive.  As for the split lines:  you'll generally
get a lot of these, even TIMER_CONTAINER has a quite a few.  I generally
prefer to move everything right of the = to the next line as that
becomes a lot more redable.