linux-kernel - Re: [PATCH v3 4/4] gpio: xilinx: Utilize for_each_set

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Date:   Thu, 30 Apr 2020 19:38:55 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Syed Nayyar Waris <syednwaris@...il.com>
Cc:     akpm@...ux-foundation.org, vilhelm.gray@...il.com,
        linus.walleij@...aro.org, bgolaszewski@...libre.com,
        michal.simek@...inx.com, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] gpio: xilinx: Utilize for_each_set_clump macro

On Thu, Apr 30, 2020 at 09:45:14PM +0530, Syed Nayyar Waris wrote:
> On Wed, Apr 29, 2020 at 01:21:14PM +0300, Andy Shevchenko wrote:
> > On Wed, Apr 29, 2020 at 04:39:47AM +0530, Syed Nayyar Waris wrote:

...

> > > +	const unsigned long state_size = BITS_PER_TYPE(*state);
> > 
> > This '*state' is unneeded complication, use BITS_PER_U32.
> > 
> > > +#define TOTAL_BITS BITS_PER_TYPE(chip->gpio_state)
> > 
> > This macro makes code uglier, besides the fact of absence of #undef.
> > And also see above.
> 
> Thank you for your review comments. Just want to clarify, you want
>  a new macro to be created - 'BITS_PER_U32' ?

It's already there (read bits.h).

> Also, don't you think that with BITS_PER_TYPE(), in case later the type
> of 'state' changes, it will be reflected in this code without any code
> change?

If it changes the bits per type will be least issues there. The rationale
behind is to have code readable. In proposed change it is not.

> Let me know if I have misunderstood something.
> 
> > 
> > > +	DECLARE_BITMAP(old, TOTAL_BITS);
> > > +	DECLARE_BITMAP(new, TOTAL_BITS);
> > > +	DECLARE_BITMAP(changed, TOTAL_BITS);

-- 
With Best Regards,
Andy Shevchenko