[question] some question about the residue
Elen Song
elen.song at atmel.com
Mon Nov 26 21:39:46 EST 2012
On 2012-11-26 18:40, Russell King - ARM Linux wrote:
> On Mon, Nov 26, 2012 at 06:37:28PM +0800, Elen Song wrote:
>> So residue actually means current active descriptor remain, it should
> No, not the current active descriptor - the transfer identified by the
> cookie, and only that transfer.
Hi Russell King:
Thank you for your explanations.
Here I got an example, perhaps you can help me figure out if it is
correct.
//allocate a cyclic transfer with 2 descriptors, a cookie identify
current transfer.
desc = dmaengine_prep_dma_cyclic(chan,
sg_dma_address,
sg_dma_len,
sg_dma_len/2,
DMA_DEV_TO_MEM);
cookie= dmaengine_submit(desc);
//if transfer in progress, state.residue is current transfer
remain(sg_dma_len remain), not current descriptor remain(sg_dma_len/2
remain).
device_tx_status(chan,cookie, &state);
Is it right?
Best Regards
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