参照元†
- struct dma_buf_attachment *db_attach
- enum dma_data_direction dma_dir
返り値†
static struct sg_table *vb2_dc_dmabuf_ops_map(
struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
{
struct vb2_dc_attachment *attach = db_attach->priv;
/* stealing dmabuf mutex to serialize map/unmap operations */
struct mutex *lock = &db_attach->dmabuf->lock;
struct sg_table *sgt;
mutex_lock(lock);
sgt = &attach->sgt;
/* return previously mapped sg table */
if (attach->dma_dir == dma_dir) {
mutex_unlock(lock);
return sgt;
}
/* release any previous cache */
if (attach->dma_dir != DMA_NONE) {
dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
attach->dma_dir);
attach->dma_dir = DMA_NONE;
}
/* mapping to the client with new direction */
sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
dma_dir);
if (!sgt->nents) {
pr_err("failed to map scatterlist\n");
mutex_unlock(lock);
return ERR_PTR(-EIO);
}
attach->dma_dir = dma_dir;
mutex_unlock(lock);
return sgt;
}
コメント†