From: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>
To: Marc Gonzalez <marc.w.gonzalez@free.fr>
Cc: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
"Antti Palosaari" <crope@iki.fi>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
linux-media <linux-media@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Bjorn Andersson" <bjorn.andersson@linaro.org>,
"Brad Love" <brad@nextdimension.cc>
Subject: Re: [PATCH v1] media: si2168: Refactor command setup code
Date: Wed, 3 Jul 2019 18:35:00 +0200 [thread overview]
Message-ID: <20190703163500.GF22408@latitude> (raw)
In-Reply-To: <6a644c94-f979-b656-472b-c7fe9303e08c@free.fr>
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Hi again,
On Wed, Jul 03, 2019 at 02:47:59PM +0200, Marc Gonzalez wrote:
> On 02/07/2019 11:51, Jonathan Neuschäfer wrote:
> > On Mon, Jul 01, 2019 at 01:44:09PM +0200, Marc Gonzalez wrote:
[...]
> >> static const struct dvb_frontend_ops si2168_ops;
> >>
> >> +#define CMD_SETUP(cmd, __args, __rlen) do { \
> >> + int wlen = sizeof(__args) - 1; \
> >> + memcpy(cmd.args, __args, wlen); \
> >> + cmd.wlen = wlen; cmd.rlen = __rlen; \
> >> +} while (0)
> >
> > It would be nice for casual readers to have a little comment here, that
> > explains (briefly) what this macro does, and what the arguments mean,
> > and their types.
>
> Just a bit of background.
>
> A macro is required /at some point/ because arrays "decay" into pointers
> when used as function arguments.
*nod*
[ I should have been more specific: By "here" I meant at that spot in
the code, and by casual readers I mostly meant casual readers of the
code once it's merged. ]
> Come to think of it, I'm really not a fan of "large" macro functions.
> I'll outline a different option in v2.
The v2 approach looks nicer to me, thanks.
> > Why cmd rather than __cmd? This seems inconsistent.
>
> Note: I hate using underscores in macro argument names, but they clashed
> with the struct field names. There was no such clash for 'cmd'.
Hmm, ok.
> > The wlen local variable can be avoided by a bit of suffling:
> >
> > #define CMD_SETUP(cmd, __args, __rlen) do { \
> > cmd.rlen = __rlen; \
> > cmd.wlen = sizeof(__args) - 1; \
> > memcpy(cmd.args, __args, cmd.wlen); \
> > } while (0)
>
> Do you think it is important to avoid a local variable?
Not exactly important, but wlen would be another name that can collide
with the name spaces of the functions where the macro is used and
trigger -Wshadow.
Greetings,
Jonathan Neuschäfer
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prev parent reply other threads:[~2019-07-03 16:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 11:44 [PATCH v1] media: si2168: Refactor command setup code Marc Gonzalez
2019-07-02 8:37 ` Marc Gonzalez
2019-07-02 9:51 ` Jonathan Neuschäfer
2019-07-03 12:47 ` Marc Gonzalez
2019-07-03 14:15 ` Marc Gonzalez
2019-07-03 16:35 ` Jonathan Neuschäfer [this message]
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