On Sun, 26 Apr 2020 at 18:04, Chun-Kuang Hu chunkuang.hu@kernel.org wrote:
Hi, Anand:
Anand K Mistry amistry@chromium.org 於 2020年4月20日 週一 下午2:09寫道：
If dma_map_sg() merges pages when creating the mapping, only the first entries will have a valid sg_dma_address() and sg_dma_len(), followed by entries with sg_dma_len() == 0.
Signed-off-by: Anand K Mistry amistry@google.com
drivers/gpu/drm/mediatek/mtk_drm_gem.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
index b04a3c2b111e09..f8fd8b98c30e3d 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c @@ -224,6 +224,9 @@ struct drm_gem_object
*mtk_gem_prime_import_sg_table(struct drm_device *dev,
expected = sg_dma_address(sg->sgl); for_each_sg(sg->sgl, s, sg->nents, i) {
if (!sg_dma_len(s))break;I think this should be 'continue'
scatterlist.h has the comment: /* * These macros should be used after a dma_map_sg call has been done * to get bus addresses of each of the SG entries and their lengths. * You should only work with the number of sg entries dma_map_sg * returns, or alternatively stop on the first sg_dma_len(sg) which * is 0. */
So breaking on the first sg_dma_len(sg) == 0 appears to be (one of) the documented approach.
Regards, Chun-Kuang.
if (sg_dma_address(s) != expected) { DRM_ERROR("sg_table is not contiguous"); ret = -EINVAL;-- 2.26.1.301.g55bc3eb7cb9-goog
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