linux-kernel - Re: [PATCH 8/8] dmaengine/dw_dmac: Add support for DMA_SLAVE

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Message-ID: <4F153D39.50206@st.com>
Date:	Tue, 17 Jan 2012 14:49:53 +0530
From:	Viresh Kumar <viresh.kumar@...com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Armando VISCONTI <armando.visconti@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	Vipin KUMAR <vipin.kumar@...com>,
	Rajeev KUMAR <rajeev-dlh.kumar@...com>,
	Deepak SIKRI <deepak.sikri@...com>,
	Vipul Kumar SAMAR <vipulkumar.samar@...com>,
	Amit VIRDI <Amit.VIRDI@...com>,
	Pratyush ANAND <pratyush.anand@...com>,
	Bhupesh SHARMA <bhupesh.sharma@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	Bhavna YADAV <bhavna.yadav@...com>,
	Vincenzo FRASCINO <Vincenzo.FRASCINO@...com>,
	Mirko GARDI <mirko.gardi@...com>
Subject: Re: [PATCH 8/8] dmaengine/dw_dmac: Add support for DMA_SLAVE_CONFIG

On 1/17/2012 2:45 PM, Viresh Kumar wrote:
>>>>>> >>> >> +      * Fix sconfig's burst size according to dw_dmac. We need to convert
>>>>>> >>> >> +      * them as: 1 -> 0, 2 -> 1, 4 -> 2, 8 -> 3, 16 -> 4.
> I need above conversion. i.e. finding bit no. of first bit set.

Something like:

unsigned int v; // 32-bit word
unsigned int r = 0;

while (v >>= 1)
{
  r++;
}

Probably find_first_bit() suits it.

-- 
viresh
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