linux-kernel - Re: [PATCH 2/2] ioatdma: add DMA

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Date:	Wed, 19 Jun 2013 10:36:50 -0700
From:	Dave Jiang <dave.jiang@...el.com>
To:	Dan Williams <djbw@...com>
CC:	Jon Mason <jon.mason@...el.com>, Vinod Koul <vinod.koul@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ioatdma: add DMA_PRIVATE capabilities flag

On 06/18/2013 05:59 PM, Dan Williams wrote:
> On Tue, Jun 18, 2013 at 5:46 PM, Jon Mason <jon.mason@...el.com> wrote:
>> Set the DMA_PRIVATE dma_transaction_type in the capability mask.  This
>> enables the ability to get an exclusive ioatdma DMA channel for any
>> devices that requests one via the dma_request_channel function call.
>>
>> Signed-off-by: Jon Mason <jon.mason@...el.com>
>> Acked-by: Dave Jiang <dave.jiang@...el.com>
>> ---
>>   drivers/dma/ioat/dma_v3.c |    1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
>> index ca6ea9b..ac2aeef 100644
>> --- a/drivers/dma/ioat/dma_v3.c
>> +++ b/drivers/dma/ioat/dma_v3.c
>> @@ -1883,6 +1883,7 @@ int ioat3_dma_probe(struct ioatdma_device *device, int dca)
>>                  dma->copy_align = 6;
>>
>>          dma_cap_set(DMA_INTERRUPT, dma->cap_mask);
>> +       dma_cap_set(DMA_PRIVATE, dma->cap_mask);
>>          dma->device_prep_dma_interrupt = ioat3_prep_interrupt_lock;
> DMA_PRIVATE here keeps all channels private, so they couldn't be used
> elsewhere, for example raid offload.  Do you need a private allocation
> or can you get away with a dynamically assigned channel?
So is there no way to reserve a channel as private if no one is using 
it? It seems the current setup is async_tx or nothing.

-- 

Dave Jiang
Application Engineer, Storage Divsion
Intel Corp.
dave.jiang@...el.com

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