Re: [PATCH v2 27/32] scsi: hisi_sas: add smp protocol support

From: John Garry
Date: Mon Nov 02 2015 - 12:04:42 EST

On 30/10/2015 16:22, John Garry wrote:
On 30/10/2015 13:53, Arnd Bergmann wrote:
On Monday 26 October 2015 22:14:58 John Garry wrote:

+ /*
+ * DMA-map SMP request, response buffers
+ */
+ /* req */
+ sg_req = &task->smp_task.smp_req;
+ elem = dma_map_sg(dev, sg_req, 1, DMA_TO_DEVICE);
+ if (!elem)
+ return -ENOMEM;
+ req_len = sg_dma_len(sg_req);
+ req_dma_addr = sg_dma_address(sg_req);

If you only use the first element, could you just use dma_map_single()?

Can do. Actually sg_req seems only ever has one element:
expander.c, smp_execute_task()
sg_init_one(&task->smp_task.smp_req, req, req_size);

I tried replacing with dma_map_single, but I feel the code is not as clean as I need to manually set sg_dma_len() and sg_dma_address():
req_len = sg_dma_len(sg_req) = sg_req->length;
sg_dma_address(sg_req) = dma_map_single(dev, sg_virt(sg_req),
req_len, DMA_TO_DEVICE);
if (dma_mapping_error(dev, sg_dma_address(sg_req)))
return -ENOMEM;
sg_dma_address(sg_req) is used in another function for unmap.


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