From mboxrd@z Thu Jan  1 00:00:00 1970
From: elen.song@atmel.com (Elen Song)
Date: Mon, 26 Nov 2012 15:35:42 +0800
Subject: [question] some question about the residue
In-Reply-To: <1353912597.7077.67.camel@vkoul-udesk3>
References: <1353912197-16616-1-git-send-email-elen.song@atmel.com>
 <1353912597.7077.67.camel@vkoul-udesk3>
Message-ID: <50B31BCE.6020100@atmel.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 2012-11-26 14:49, Vinod Koul wrote:
> On Mon, 2012-11-26 at 14:43 +0800, Elen Song wrote:
>> Hi All:
>>
>> 	I got a question about the residue in struct dma_tx_state:
>>
>> 	I wonder what residue means, is it the current descriptor residue or
>>
>> 	the total dma buffer residue?
> You read the status for descriptor, so it means this is residue for said
> descriptor.
>
>
Hi Koul:

Well , I don't get it , if I read the status of a LLI, is it means the 
residue of total LLI length?

I saw driver/dma/amba-pl08x.c drivers/dma/coh901318.c, if read status of 
a LLI, residue is the remain of LLI, not only
current descriptor.

1 patch from Russel King how he realize device_tx_status said:

[PATCH] ARM: PL08x: clean up LLI lookup
As the LLI list is an array, we can use maths to locate which LLI
index we're currently at, and then sum up the remaining LLI entries
until we reach the end of the list.

Is it right?

best regards