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

[John Garry]

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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