vmalloc_sg: make sure all pages in vmalloc area are really DMA-ready

Hi linux-media devs, this is similar to one of HCH's patches that hasn't been applied yet.

The patch 7b4eeed174b7: "[media] vmalloc_sg: make sure all pages in vmalloc area are really DMA-ready" from Jun 12, 2014, leads to the following static checker warning:

drivers/media/v4l2-core/videobuf-dma-sg.c:236 videobuf_dma_init_kernel()
error: 'addr' came from dma_alloc_coherent() so we can't do virt_to_phys()

drivers/media/v4l2-core/videobuf-dma-sg.c
210 static int videobuf_dma_init_kernel(struct videobuf_dmabuf *dma, int direction,
211 int nr_pages)
212 {
213 int i;
214
215 dprintk(1, "init kernel [%d pages]\n", nr_pages);
216
217 dma->direction = direction;
218 dma->vaddr_pages = kcalloc(nr_pages, sizeof(*dma->vaddr_pages),
219 GFP_KERNEL);
220 if (!dma->vaddr_pages)
221 return -ENOMEM;
222
223 dma->dma_addr = kcalloc(nr_pages, sizeof(*dma->dma_addr), GFP_KERNEL);
224 if (!dma->dma_addr) {
225 kfree(dma->vaddr_pages);
226 return -ENOMEM;
227 }
228 for (i = 0; i < nr_pages; i++) {
229 void *addr;
230
231 addr = dma_alloc_coherent(dma->dev, PAGE_SIZE,

                        ^^^^^^^^^^^^^^^^^^^^^^^^^

232 &(dma->dma_addr[i]), GFP_KERNEL);
233 if (addr == NULL)
234 goto out_free_pages;
235

   236                  dma->vaddr_pages[i] = virt_to_page(addr);
                                              ^^^^^^^^^^^^^^^^^^

Apparently this isn't allowed.

   237          }
   238          dma->vaddr = vmap(dma->vaddr_pages, nr_pages, VM_MAP | VM_IOREMAP,
   239                            PAGE_KERNEL);
   240          if (NULL == dma->vaddr) {
   241                  dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
   242                  goto out_free_pages;
   243          }
   244  
   245          dprintk(1, "vmalloc is at addr %p, size=%d\n",
   246                  dma->vaddr, nr_pages << PAGE_SHIFT);
   247  
   248          memset(dma->vaddr, 0, nr_pages << PAGE_SHIFT);
   249          dma->nr_pages = nr_pages;
   250  
   251          return 0;
   252  out_free_pages:
   253          while (i > 0) {
   254                  void *addr;

regards,
dan carpenter