drm/prime: make the pages array optional for drm_prime_sg_to_page_addr_arrays

/**

 * 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;