linux-kernel - Re: [PATCH] staging: s5k3e2fx.c: simplify complexity by factoring

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Date:	Fri, 18 Dec 2009 10:41:46 -0800
From:	Greg KH <greg@...ah.com>
To:	Justin Madru <jdm64@...ab.com>
Cc:	linux-kernel@...r.kernel.org, gregkh@...e.de, error27@...il.com,
	ray-lk@...rabbit.org
Subject: Re: [PATCH] staging: s5k3e2fx.c: simplify complexity by factoring

On Tue, Dec 15, 2009 at 12:52:10PM -0800, Justin Madru wrote:
> the code was looping, seting s_move[i] to the following calculations
> 
> if (actual_step >= 0)
>         s_move[i] = ((((i + 1) * gain + 0x200) - (i * gain + 0x200)) / 0x400);
> else
>         s_move[i] = ((((i + 1) * gain - 0x200) - (i * gain - 0x200)) / 0x400);
> 
> but, this code redues to the expression
> 	s_move[i] = gain >> 10;
> 
> The reason for the complexity was to generate a step function with
> integer division and rounding to land on specific values. But these calculations
> can be simplified to the following code:
> 
> 	gain = ((actual_step << 10) / 5) >> 10;
> 	for (i = 0; i <= 4; i++)
> 		s_move[i] = gain;

Care to resend this with a Signed-off-by: line, and add the reviewed-by
line that was requested by Ray?

thanks,

greg k-h
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