drm/prime: introduce sg->pages/addr arrays helper

the ttm drivers need this currently, in order to get fault handling
working and efficient.

It also allows addrs to be NULL for devices like udl.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1bdf2b54eaf6..20dbf2c45385 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -227,6 +227,42 @@ out:
 }
 EXPORT_SYMBOL(drm_prime_pages_to_sg);
 
+/* export 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)
+{
+        unsigned count;
+        struct scatterlist *sg;
+        struct page *page;
+        u32 len, offset;
+        int pg_index;
+        dma_addr_t addr;
+
+        pg_index = 0;
+        for_each_sg(sgt->sgl, sg, sgt->nents, count) {
+                len = sg->length;
+                offset = sg->offset;
+                page = sg_page(sg);
+                addr = sg_dma_address(sg);
+
+                while (len > 0) {
+                        if (WARN_ON(pg_index >= max_pages))
+                                return -1;
+                        pages[pg_index] = page;
+                        if (addrs)
+                                addrs[pg_index] = addr;
+
+                        page++;
+                        addr += PAGE_SIZE;
+                        len -= PAGE_SIZE;
+                        pg_index++;
+                }
+        }
+        return 0;
+}
+EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
 /* helper function to cleanup a GEM/prime object */
 void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg)
 {