On 2020-08-26 07:32, Marek Szyprowski wrote:
Replace the current hand-crafted code for extracting pages and DMA
addresses from the given scatterlist by the much more robust
code based on the generic scatterlist iterators and recently
introduced sg_table-based wrappers. The resulting code is simple and
easy to understand, so the comment describing the old code is no
longer needed.
Is removing the WARN_ON()s intentional? It certainly seems like it would
be a genuine driver bug if the caller asked for addresses but didn't
allocate appropriately-sized arrays. Might be worth noting either way.
I'm also assuming this isn't called in performance-critical paths with
massive lists such that the two separate iterations might have a
noticeable impact.
Nits aside,
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
---
drivers/gpu/drm/drm_prime.c | 49 ++++++++++++-------------------------
1 file changed, 15 insertions(+), 34 deletions(-)
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 4ed5ed1f078c..5d181bf60a44 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -990,45 +990,26 @@ EXPORT_SYMBOL(drm_gem_prime_import);
int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
dma_addr_t *addrs, int max_entries)
{
- unsigned count;
- struct scatterlist *sg;
- struct page *page;
- u32 page_len, page_index;
- dma_addr_t addr;
- u32 dma_len, dma_index;
-
- /*
- * Scatterlist elements contains both pages and DMA addresses, but
- * one shoud not assume 1:1 relation between them. The sg->length is
- * the size of the physical memory chunk described by the sg->page,
- * while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk
- * described by the sg_dma_address(sg).
- */
- page_index = 0;
- dma_index = 0;
- for_each_sg(sgt->sgl, sg, sgt->nents, count) {
- page_len = sg->length;
- page = sg_page(sg);
- dma_len = sg_dma_len(sg);
- addr = sg_dma_address(sg);
-
- while (pages && page_len > 0) {
- if (WARN_ON(page_index >= max_entries))
+ struct sg_dma_page_iter dma_iter;
+ struct sg_page_iter page_iter;
+ struct page **p = pages;
+ dma_addr_t *a = addrs;
+
+ if (pages) {
+ for_each_sgtable_page(sgt, &page_iter, 0) {
+ if (p - pages >= max_entries)
return -1;
- pages[page_index] = page;
- page++;
- page_len -= PAGE_SIZE;
- page_index++;
+ *p++ = sg_page_iter_page(&page_iter);
}
- while (addrs && dma_len > 0) {
- if (WARN_ON(dma_index >= max_entries))
+ }
+ if (addrs) {
+ for_each_sgtable_dma_page(sgt, &dma_iter, 0) {
+ if (a - addrs >= max_entries)
return -1;
- addrs[dma_index] = addr;
- addr += PAGE_SIZE;
- dma_len -= PAGE_SIZE;
- dma_index++;
+ *a++ = sg_page_iter_dma_address(&dma_iter);
}
}
+
return 0;
}
EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
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