linux-kernel - Re: [PATCH 08/32] dmaengine: ste_dma40: Optimise local MAX() macro

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Message-Id: <201304181246.03357.arnd@arndb.de>
Date:	Thu, 18 Apr 2013 12:46:03 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linus.walleij@...ricsson.com, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <djbw@...com>,
	Per Forlin <per.forlin@...ricsson.com>,
	Rabin Vincent <rabin@....in>
Subject: Re: [PATCH 08/32] dmaengine: ste_dma40: Optimise local MAX() macro

On Thursday 18 April 2013, Lee Jones wrote:
> The current implementation of the DMA40's local MAX() macro evaluates
> its arguments more times than is necessary. This patch strips it
> optimises it to only evaluate what's appropriate.

No, it does not.

> index b21a8a3..7b451b2 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -53,7 +53,7 @@
>  #define D40_ALLOC_PHY          BIT(30)
>  #define D40_ALLOC_LOG_FREE     BIT(0)
>  
> -#define MAX(a, b) (((a) < (b)) ? (b) : (a))
> +#define MAX(a, b) ((a > b) ? a : b)

This just makes the macro worse in case you pass a complex expression
in, which can now have additional unwanted effects. Just drop this patch.

	Arnd
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