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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>
This commit is contained in:
Marek Szyprowski 2020-05-08 16:04:44 +02:00
parent 9123e3a74e
commit d46e7ae24b
3 changed files with 36 additions and 20 deletions
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23
drivers/gpu/drm/drm_gem_cma_helper.c
View File

@ -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);

31
drivers/gpu/drm/drm_prime.c
View File

@ -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

2
include/drm/drm_prime.h
View File

@ -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,