linux-kernel - Re: [PATCH v5] Driver for ON Semi AR0521 camera sensor

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Date:   Sat, 9 Oct 2021 13:18:50 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Krzysztof Hałasa <khalasa@...p.pl>,
        "joe@...ches.com" <joe@...ches.com>
Cc:     Sakari Ailus <sakari.ailus@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH v5] Driver for ON Semi AR0521 camera sensor

On 10/9/21 2:07 AM, Jacopo Mondi wrote:
> Hi Krzysztof,
> 
>     I've been testing this driver in the last few days, thanks for your
> effort in upstreaming it!
> 
> I'll separately comment on what I had to change to have it working for
> my use case, but let me continue the discussion from where it was left
> pending here to add my 2 cents.
> 
> On Thu, Oct 07, 2021 at 11:11:09AM +0200, Krzysztof Hałasa wrote:
>> Hi Sakari,
>>
>> Thanks for your input.
>>
>>> Where's the corresponding DT binding patch? Ideally it would be part of the
>>> same set.
>>
>> Well I've sent it a moment before this one. Will make them a set next
>> time.
>>
>>>> +#define AR0521_WIDTH_BLANKING_MIN     572u
>>>> +#define AR0521_HEIGHT_BLANKING_MIN     28u // must be even
>>>
>>> Please use /* */ for comments. The SPDX tag is an exception.
>>
>> As far as I know, this is no longer the case, the C99 comments are now
>> permitted and maybe even encouraged. Or was I dreaming?
>>
>> checkpatch doesn't protest either.
> 
> To my understanding the C99 standard added support for the //
> commenting style and tollerate them, but they're still from C++ and I
> see very few places where they're used in the kernel, and per as far I
> know they're still not allowed by the coding style
> https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting

http://lkml.iu.edu/hypermail/linux/kernel/1607.1/00627.html

Maybe we should update coding-style then.

> 
> Looking at how you used comments in the driver I think you could get
> rid of most // comments easily, the register tables might be an
> exception but I would really try to remove them from there as well.
> 
> 
>>
>>> Please wrap your lines at 80 or earlier, unless a sound reason exists to do
>>> otherwise.
>>
>> This limitation appears to be lifted as well, after all those years.
>> Is there a specific reason to still use it here? Yes, lines longer than
>> 80 chars make the code much more readable (for my eyes, at least).
>> Yes, I know there is some "soft" limit, and I trim lines when it makes
>> them better in my opinion.
>>
> 
> In my personal opinion lifting that restriction caused more pain than
> anything, as different subsystem are now imposing different
> requirements. Here everything has been so far pretty strict about
> going over 80-cols, but I think there are situation where it makes
> sense in example
> 

[snip]

> 
> My suggestion is: aim to 80 cols whenever possible, if it forces you
> to do things like the above shown function declaration you can go a
> little over that

Yes, 80 max is still preferred. Up to 100 may be tolerable in some
cases.

> As reported here
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144
> if you go over 100 you should ask yourself what are you doing :)




-- 
~Randy