drm: prime: add common helper to check scatterlist contiguity

It is a common operation done by DRM drivers to check the contiguity
of the DMA-mapped buffer described by a scatterlist in the
sg_table object. Let's add a common helper for this operation.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index 822edea..59b9ca2 100644 (file)
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -471,26 +471,9 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
 {
        struct drm_gem_cma_object *cma_obj;
 
-       if (sgt->nents != 1) {
-               /* check if the entries in the sg_table are contiguous */
-               dma_addr_t next_addr = sg_dma_address(sgt->sgl);
-               struct scatterlist *s;
-               unsigned int i;
-
-               for_each_sg(sgt->sgl, s, sgt->nents, i) {
-                       /*
-                        * sg_dma_address(s) is only valid for entries
-                        * that have sg_dma_len(s) != 0
-                        */
-                       if (!sg_dma_len(s))
-                               continue;
-
-                       if (sg_dma_address(s) != next_addr)
-                               return ERR_PTR(-EINVAL);
-
-                       next_addr = sg_dma_address(s) + sg_dma_len(s);
-               }
-       }
+       /* check if the entries in the sg_table are contiguous */
+       if (drm_prime_get_contiguous_size(sgt) < attach->dmabuf->size)
+               return ERR_PTR(-EINVAL);
 
        /* Create a CMA GEM buffer. */
        cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size);

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1693aa7..4ed5ed1 100644 (file)
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -826,6 +826,37 @@ out:
 EXPORT_SYMBOL(drm_prime_pages_to_sg);
 
 /**
+ * drm_prime_get_contiguous_size - returns the contiguous size of the buffer
+ * @sgt: sg_table describing the buffer to check
+ *
+ * This helper calculates the contiguous size in the DMA address space
+ * of the the buffer described by the provided sg_table.
+ *
+ * This is useful for implementing
+ * &drm_gem_object_funcs.gem_prime_import_sg_table.
+ */
+unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt)
+{
+       dma_addr_t expected = sg_dma_address(sgt->sgl);
+       struct scatterlist *sg;
+       unsigned long size = 0;
+       int i;
+
+       for_each_sgtable_dma_sg(sgt, sg, i) {
+               unsigned int len = sg_dma_len(sg);
+
+               if (!len)
+                       break;
+               if (sg_dma_address(sg) != expected)
+                       break;
+               expected += len;
+               size += len;
+       }
+       return size;
+}
+EXPORT_SYMBOL(drm_prime_get_contiguous_size);
+
+/**
  * drm_gem_prime_export - helper library implementation of the export callback
  * @obj: GEM object to export
  * @flags: flags like DRM_CLOEXEC and DRM_RDWR

diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
index 9af7422..47ef116 100644 (file)
--- a/include/drm/drm_prime.h
+++ b/include/drm/drm_prime.h
@@ -92,6 +92,8 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page
 struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
                                     int flags);
 
+unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt);
+
 /* helper functions for importing */
 struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
                                                struct dma_buf *dma_buf,