From: Matthias Schwarzott <zzam@gentoo.org>
To: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Marc Gonzalez <marc.w.gonzalez@free.fr>
Cc: "Brad Love" <brad@nextdimension.cc>,
"Antti Palosaari" <crope@iki.fi>,
"Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
linux-media <linux-media@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
MSM <linux-arm-msm@vger.kernel.org>,
"Bjorn Andersson" <bjorn.andersson@linaro.org>
Subject: Re: [PATCH v3] media: si2168: Refactor command setup code
Date: Sun, 14 Jul 2019 20:31:18 +0200 [thread overview]
Message-ID: <13f74614-69b8-00e1-2072-ba390d5aa2cb@gentoo.org> (raw)
In-Reply-To: <20190713070256.3495de51@coco.lan>
Am 13.07.19 um 12:02 schrieb Mauro Carvalho Chehab:
> Em Sat, 13 Jul 2019 00:11:12 +0200
> Marc Gonzalez <marc.w.gonzalez@free.fr> escreveu:
>
>> On 12/07/2019 19:45, Mauro Carvalho Chehab wrote:
>>
>>> Brad Love <brad@nextdimension.cc> escreveu:
>>>
>>> IMHO, using sizeof() here is a very bad idea.
>>
>> You may have a point...
>> (Though I'm not proposing a kernel API function, merely code
>> refactoring for a single file that's unlikely to change going
>> forward.)
>
> Yes, I know, but we had already some bugs due to the usage of
> sizeof() on similar macros at drivers in the past.
>
>> It's also bad form to repeat the cmd size (twice) when the compiler
>> can figure it out automatically for string literals (which is 95%
>> of the use-cases).
>>
>> I can drop the macro, and just use the helper...
>
> The helper function sounds fine.
>
>>
>> Or maybe there's a GCC extension to test that an argument is a
>> string literal...
>
> If this could be evaluated by some advanced macro logic that
> would work not only with gcc but also with clang, then a
> macro that does what you proposed could be useful.
>
> There are some ways to check the type of a macro argument, but I'm
> not sure if are there any way for it to distinguish between a
> string constant from a char * array.
>
Maybe something like this will prevent compilation if the argument is no
string literal:
#define CMD_SETUP(cmd, args, rlen) \
cmd_setup(cmd, args "", sizeof(args) - 1, rlen)
Another idea is a check like:
#define CMD_SETUP(cmd, args, rlen) \
do { \
BUILD_BUG_ON(#args[0] != "\""); \
cmd_setup(cmd, args "", sizeof(args) - 1, rlen) \
} while(0)
Regards
Matthias
next prev parent reply other threads:[~2019-07-14 18:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-04 10:33 [PATCH v3] media: si2168: Refactor command setup code Marc Gonzalez
2019-07-12 8:43 ` Uwe Kleine-König
2019-07-12 9:37 ` Marc Gonzalez
2019-07-12 15:47 ` Brad Love
2019-07-12 17:45 ` Mauro Carvalho Chehab
2019-07-12 22:11 ` Marc Gonzalez
2019-07-13 10:02 ` Mauro Carvalho Chehab
2019-07-14 18:31 ` Matthias Schwarzott [this message]
2019-07-12 21:41 ` Marc Gonzalez
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