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

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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.

opinion?


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.



cheers,
John

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