linux-kernel - Re: [PATCH 05/32] dmaengine: ste_dma40: Supply macros to resolve 'src' and 'dst' directions

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Message-ID: <CACRpkdYD21VEHZ2825=e7PnATp-tfrL2rg4rKboG-Fq04U162A@mail.gmail.com>
Date:	Thu, 25 Apr 2013 10:22:13 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rabin Vincent <rabin@....in>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	Arnd Bergmann <arnd@...db.de>,
	Vinod Koul <vinod.koul@...el.com>,
	Per Forlin <per.forlin@...ricsson.com>,
	Dan Williams <djbw@...com>
Subject: Re: [PATCH 05/32] dmaengine: ste_dma40: Supply macros to resolve
 'src' and 'dst' directions

On Thu, Apr 18, 2013 at 12:11 PM, Lee Jones <lee.jones@...aro.org> wrote:

> There are lots of lengthy if() statements located sporadically up and
> down the driver. This simple macro should make many of them a little
> simpler to decipher. The remainder have to stay in place, as they
> detail slightly more specific settings.
>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Dan Williams <djbw@...com>
> Cc: Per Forlin <per.forlin@...ricsson.com>
> Cc: Rabin Vincent <rabin@....in>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
(...)

> +#define D40_IS_SRC(dir)  ((dir == STEDMA40_PERIPH_TO_MEM) ? true : false)

And when I reas the code and see D40_IS_SRC, what does that
mean? That the channel is a source of .. what exactly?

The older explicit comparison would be more informative.

> +#define D40_IS_DST(dir) (((dir == STEDMA40_MEM_TO_PERIPH) || \
> +                         (dir == STEDMA40_MEM_TO_MEM)) ? true : false)
> +

The comparison to STEDMA40_MEM_TO_MEM is unintelligible, if I see
that macro it has a very unintuitive name, since it is not just
DST but also SRC.

The latter macro would be named somthing like D40_IS_DST_OR_MEM2MEM
and then it will not simplify the code very much.

You need to come up with something different here, this is just making the
driver harder to understand.

I think this patch should be just dropped.

Yours,
Linus Walleij
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