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 <[email protected]>
Reviewed-by: Andrzej Hajda <[email protected]>
Reviewed-by: Robin Murphy <[email protected]>
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1693aa7..4ed5ed1 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -826,6 +826,37 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page
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
