Commit d46e7ae2 authored by Marek Szyprowski's avatar Marek Szyprowski
Browse files

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: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: default avatarAndrzej Hajda <a.hajda@samsung.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
parent 9123e3a7

drivers/gpu/drm/drm_gem_cma_helper.c

+3 −20
Original line number Diff line number Diff line
@@ -471,27 +471,10 @@ 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)

	if (drm_prime_get_contiguous_size(sgt) < attach->dmabuf->size)

		return ERR_PTR(-EINVAL);



			next_addr = sg_dma_address(s) + sg_dma_len(s);

		}

	}



	/* Create a CMA GEM buffer. */

	cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size);

	if (IS_ERR(cma_obj))

drivers/gpu/drm/drm_prime.c

+31 −0
Original line number Diff line number Diff line
@@ -825,6 +825,37 @@ 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

include/drm/drm_prime.h

+2 −0
Original line number Diff line number Diff line
@@ -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,

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