linux-kernel - Re: [PATCH] Staging: panel: Fixed a macro coding style issue

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Date:	Thu, 20 Sep 2012 11:09:20 +0530
From:	Adil Mujeeb <mujeeb.adil@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	Joe Perches <joe@...ches.com>, gregkh@...uxfoundation.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: panel: Fixed a macro coding style issue

Hi,

On Thu, Sep 20, 2012 at 10:52 AM, Willy Tarreau <w@....eu> wrote:
> On Thu, Sep 20, 2012 at 09:19:42AM +0530, Adil Mujeeb wrote:
>> On Thu, Sep 20, 2012 at 2:09 AM, Willy Tarreau <w@....eu> wrote:
>> > On Wed, Sep 19, 2012 at 12:44:58PM -0700, Joe Perches wrote:
>> >> On Thu, 2012-09-20 at 01:07 +0530, Adil Mujeeb wrote:
>> >> > Removed do {} while (0) loop for a single statement macros
>> >> >
>> >> > Signed-off-by: Adil Mujeeb <mujeeb.adil@...il.com>
>> >> > ---
>> >> >  linux-3.6-rc6/drivers/staging/panel/panel.c |    4 ++--
>> >> >  1 files changed, 2 insertions(+), 2 deletions(-)
>> >> >
>> >> > diff --git a/linux-3.6-rc6/drivers/staging/panel/panel.c b/linux-3.6-rc6/drivers/staging/panel/panel.c
>> >> > index 39f9982..d9fec5b 100644
>> >> > --- a/linux-3.6-rc6/drivers/staging/panel/panel.c
>> >> > +++ b/linux-3.6-rc6/drivers/staging/panel/panel.c
>> >> > @@ -137,8 +137,8 @@
>> >> >  #define r_ctr(x)        (parport_read_control((x)->port))
>> >> >  #define r_dtr(x)        (parport_read_data((x)->port))
>> >> >  #define r_str(x)        (parport_read_status((x)->port))
>> >> > -#define w_ctr(x, y)     do { parport_write_control((x)->port, (y)); } while (0)
>> >> > -#define w_dtr(x, y)     do { parport_write_data((x)->port, (y)); } while (0)
>> >> > +#define w_ctr(x, y)     (parport_write_control((x)->port, (y)))
>> >> > +#define w_dtr(x, y)     (parport_write_data((x)->port, (y)))
>> >>
>> >> Unnecessary parentheses too.
>> >> It might be better to use static inlines instead.
>>
>> I just did this change only as per checkpatch script warning. Also the
>> parentheses is added similar to other macros.
>> So should i removed all the macros and convert it to static inlines ?
>>
>> > Agreed. We already got bugs in the cyrix register manipulation for
>> > years because of the use of macros which caused registers to be set
>> > in the wrong order, let's not redo that mistake again.
>>
>> hmmm macros seems too dangerous but does it mean we should not use
>> macros altogether?
>
> As long as we can easily replace them with static inline, we should
> avoid them. They're pretty useful for many things (eg: type-agnostic
> data manipulation) but what you see above does not provide much value
> in my opinion. And I wrote this something like 10 years ago but since
> then I learned from my mistakes :-)

Thanks for sharing :)

>> So should i create a single patch which replaces all macros of this
>> file into inline function?
>
> It might be possible, but what are you trying to do ? If it's just a
> minor cleanup patch, there is always the risk of breaking something
> for zero value added. This driver needs a major lifting, it needs to
> be cut into smaller functions for example. Maybe this is something
> you should try to do instead of just changing a few defines ?

Yes I was just doing minor cleanup and one of TODO item.

> Also, do you have such a device to test your changes ?

No I dont have.

>> This is my first effort in submitting a patch :)
>
> You're welcome in this effort, but you should be very careful.
> Playing with driver code is fun and addictive, but that breaks much
> faster than you can imagine and it becomes frustrating to see your
> cleanup patch reverted two days after its inclusion.

Thanks for advice, I'll keep this in mind while doing the changes next time :)

Regards,
Adil

>
> Regards,
> Willy
>
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