drm/prime: make the pages array optional for drm_prime_sg_to_page_addr_arrays

Most of the time we only need the dma addresses.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Roger He <Hongbo.He@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180227115000.4105-2-christian.koenig@amd.com
Link: https://patchwork.freedesktop.org/patch/msgid/20180227115000.4105-3-christian.koenig@amd.com
Link: https://patchwork.freedesktop.org/patch/msgid/20180227115000.4105-4-christian.koenig@amd.com
Link: https://patchwork.freedesktop.org/patch/msgid/20180227115000.4105-5-christian.koenig@amd.com
Link: https://patchwork.freedesktop.org/patch/msgid/BN6PR12MB18262C0DE9B5F07B9A42EAE7F2C60@BN6PR12MB1826.namprd12.prod.outlook.com

drivers/gpu/drm/drm_prime.c

@@ -922,40 +922,40 @@ EXPORT_SYMBOL(drm_prime_pages_to_sg);
 /**
  * drm_prime_sg_to_page_addr_arrays - convert an sg table into a page array
  * @sgt: scatter-gather table to convert
- * @pages: array of page pointers to store the page array in
+ * @pages: optional array of page pointers to store the page array in
  * @addrs: optional array to store the dma bus address of each page
- * @max_pages: size of both the passed-in arrays
+ * @max_entries: size of both the passed-in arrays
  *
  * Exports an sg table into an array of pages and addresses. This is currently
  * required by the TTM driver in order to do correct fault handling.
  */
 int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
-				     dma_addr_t *addrs, int max_pages)
+				     dma_addr_t *addrs, int max_entries)
 {
 	unsigned count;
 	struct scatterlist *sg;
 	struct page *page;
-	u32 len;
-	int pg_index;
+	u32 len, index;
 	dma_addr_t addr;
 
-	pg_index = 0;
+	index = 0;
 	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
 		len = sg->length;
 		page = sg_page(sg);
 		addr = sg_dma_address(sg);
 
 		while (len > 0) {
-			if (WARN_ON(pg_index >= max_pages))
+			if (WARN_ON(index >= max_entries))
 				return -1;
-			pages[pg_index] = page;
+			if (pages)
+				pages[index] = page;
 			if (addrs)
-				addrs[pg_index] = addr;
+				addrs[index] = addr;
 
 			page++;
 			addr += PAGE_SIZE;
 			len -= PAGE_SIZE;
-			pg_index++;
+			index++;
 		}
 	}
 	return 0;