drm/prime: split array import functions v4

Mapping the imported pages of a DMA-buf into an userspace process
doesn't work as expected.

But we have reoccurring requests on this approach, so split the
functions for this and  document that dma_buf_mmap() needs to be used
instead.

v2: split it into two functions
v3: rebased on latest changes
v4: update commit message a bit

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/403838/

1 files changed, 39 insertions, 25 deletions

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 7db55fce35d8..683aa29ecd3b 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -978,44 +978,58 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 EXPORT_SYMBOL(drm_gem_prime_import);
 
 /**
- * drm_prime_sg_to_page_addr_arrays - convert an sg table into a page array
+ * drm_prime_sg_to_page_array - convert an sg table into a page array
  * @sgt: scatter-gather table to convert
- * @pages: optional array of page pointers to store the page array in
- * @addrs: optional array to store the dma bus address of each page
+ * @pages: array of page pointers to store the pages in
+ * @max_entries: size of the passed-in array
+ *
+ * Exports an sg table into an array of pages.
+ *
+ * This function is deprecated and strongly discouraged to be used.
+ * The page array is only useful for page faults and those can corrupt fields
+ * in the struct page if they are not handled by the exporting driver.
+ */
+int __deprecated drm_prime_sg_to_page_array(struct sg_table *sgt,
+					    struct page **pages,
+					    int max_entries)
+{
+	struct sg_page_iter page_iter;
+	struct page **p = pages;
+
+	for_each_sgtable_page(sgt, &page_iter, 0) {
+		if (WARN_ON(p - pages >= max_entries))
+			return -1;
+		*p++ = sg_page_iter_page(&page_iter);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(drm_prime_sg_to_page_array);
+
+/**
+ * drm_prime_sg_to_dma_addr_array - convert an sg table into a dma addr array
+ * @sgt: scatter-gather table to convert
+ * @addrs: array to store the dma bus address of each page
  * @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.
+ * Exports an sg table into an array of addresses.
  *
- * Drivers can use this in their &drm_driver.gem_prime_import_sg_table
+ * Drivers should use this in their &drm_driver.gem_prime_import_sg_table
  * implementation.
  */
-int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
-				     dma_addr_t *addrs, int max_entries)
+int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs,
+				   int max_entries)
 {
 	struct sg_dma_page_iter dma_iter;
-	struct sg_page_iter page_iter;
-	struct page **p = pages;
 	dma_addr_t *a = addrs;
 
-	if (pages) {
-		for_each_sgtable_page(sgt, &page_iter, 0) {
-			if (WARN_ON(p - pages >= max_entries))
-				return -1;
-			*p++ = sg_page_iter_page(&page_iter);
-		}
-	}
-	if (addrs) {
-		for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
-			if (WARN_ON(a - addrs >= max_entries))
-				return -1;
-			*a++ = sg_page_iter_dma_address(&dma_iter);
-		}
+	for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
+		if (WARN_ON(a - addrs >= max_entries))
+			return -1;
+		*a++ = sg_page_iter_dma_address(&dma_iter);
 	}
-
 	return 0;
 }
-EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
+EXPORT_SYMBOL(drm_prime_sg_to_dma_addr_array);
 
 /**
  * drm_prime_gem_destroy - helper to clean up a PRIME-imported GEM object