From: Leon Romanovsky <leon@kernel.org>
To: Xie He <xie.he.0141@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Linux X25 <linux-x25@vger.kernel.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Martin Schiller <ms@dev.tdt.de>, Krzysztof Halasa <khc@pm.waw.pl>
Subject: Re: [PATCH net-next RFC v3] net: hdlc_x25: Queue outgoing LAPB frames
Date: Tue, 16 Feb 2021 09:39:58 +0200 [thread overview]
Message-ID: <YCt2zmL3GiPodutc@unreal> (raw)
In-Reply-To: <CAJht_ENDJ-T_9-V04YUP-Qp+PnZnAcOeV+6eUXkTX4pmm5Vrag@mail.gmail.com>
On Mon, Feb 15, 2021 at 11:30:25PM -0800, Xie He wrote:
> On Mon, Feb 15, 2021 at 10:04 PM Leon Romanovsky <leon@kernel.org> wrote:
> >
> > On Mon, Feb 15, 2021 at 11:08:02AM -0800, Xie He wrote:
> > > On Mon, Feb 15, 2021 at 10:54 AM Leon Romanovsky <leon@kernel.org> wrote:
> > > >
> > > > On Mon, Feb 15, 2021 at 09:23:32AM -0800, Xie He wrote:
> > > > > On Mon, Feb 15, 2021 at 1:25 AM Leon Romanovsky <leon@kernel.org> wrote:
> > > > > >
> > > > > > > + /* When transmitting data:
> > > > > > > + * first we'll remove a pseudo header of 1 byte,
> > > > > > > + * then the LAPB module will prepend an LAPB header of at most 3 bytes.
> > > > > > > + */
> > > > > > > + dev->needed_headroom = 3 - 1;
> > > > > >
> > > > > > 3 - 1 = 2
> > > > > >
> > > > > > Thanks
> > > > >
> > > > > Actually this is intentional. It makes the numbers more meaningful.
> > > > >
> > > > > The compiler should automatically generate the "2" so there would be
> > > > > no runtime penalty.
> > > >
> > > > If you want it intentional, write it in the comment.
> > > >
> > > > /* When transmitting data, we will need extra 2 bytes headroom,
> > > > * which are 3 bytes of LAPB header minus one byte of pseudo header.
> > > > */
> > > > dev->needed_headroom = 2;
> > >
> > > I think this is unnecessary. The current comment already explains the
> > > meaning of the "1" and the "3". There's no need for a reader of this
> > > code to understand what a "2" is. That is the job of the compiler, not
> > > the human reader.
> >
> > It is not related to compiler/human format. If you need to write "3 - 1"
> > to make it easy for users, it means that your comment above is not
> > full/correct/e.t.c.
>
> My point is: there is no need for human programmers / code readers to
> understand what this "2" is. There is no need to explain what this "2"
> means in the comment. There is no need to write this "2" in the code.
> There is no need for this "2" to appear anywhere. That is just an
> intermediate result generated by the compiler. It is similar to
> assembly or machine code. It is generated by the compiler. Human
> programmers just don't care about this intermediate result.
>
> My point could be more apparent if you consider a more complex
> situation: "3 - 1 + 2 + 4 + 2". No human would want to see a
> meaningless "10" in the code. We want to see the meaning of the
> numbers, not a meaningless intermediate calculation result.
Right, and we are using defines for that.
Thanks
prev parent reply other threads:[~2021-02-16 7:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-15 7:27 [PATCH net-next RFC v3] net: hdlc_x25: Queue outgoing LAPB frames Xie He
2021-02-15 9:24 ` Leon Romanovsky
2021-02-15 17:23 ` Xie He
2021-02-15 18:54 ` Leon Romanovsky
2021-02-15 19:08 ` Xie He
2021-02-16 6:03 ` Leon Romanovsky
2021-02-16 7:30 ` Xie He
2021-02-16 7:39 ` Leon Romanovsky [this message]
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