[media] vb2-dma-sg: add support for dmabuf exports

Add DMABUF export support to vb2-dma-sg.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 170 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 81e88a067882..0566e94a5a1d 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -408,6 +408,175 @@ static int vb2_dma_sg_mmap(void *buf_priv, struct vm_area_struct *vma)
 }
 
 /*********************************************/
+/*         DMABUF ops for exporters          */
+/*********************************************/
+
+struct vb2_dma_sg_attachment {
+        struct sg_table sgt;
+        enum dma_data_direction dma_dir;
+};
+
+static int vb2_dma_sg_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
+        struct dma_buf_attachment *dbuf_attach)
+{
+        struct vb2_dma_sg_attachment *attach;
+        unsigned int i;
+        struct scatterlist *rd, *wr;
+        struct sg_table *sgt;
+        struct vb2_dma_sg_buf *buf = dbuf->priv;
+        int ret;
+
+        attach = kzalloc(sizeof(*attach), GFP_KERNEL);
+        if (!attach)
+                return -ENOMEM;
+
+        sgt = &attach->sgt;
+        /* Copy the buf->base_sgt scatter list to the attachment, as we can't
+         * map the same scatter list to multiple attachments at the same time.
+         */
+        ret = sg_alloc_table(sgt, buf->dma_sgt->orig_nents, GFP_KERNEL);
+        if (ret) {
+                kfree(attach);
+                return -ENOMEM;
+        }
+
+        rd = buf->dma_sgt->sgl;
+        wr = sgt->sgl;
+        for (i = 0; i < sgt->orig_nents; ++i) {
+                sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
+                rd = sg_next(rd);
+                wr = sg_next(wr);
+        }
+
+        attach->dma_dir = DMA_NONE;
+        dbuf_attach->priv = attach;
+
+        return 0;
+}
+
+static void vb2_dma_sg_dmabuf_ops_detach(struct dma_buf *dbuf,
+        struct dma_buf_attachment *db_attach)
+{
+        struct vb2_dma_sg_attachment *attach = db_attach->priv;
+        struct sg_table *sgt;
+
+        if (!attach)
+                return;
+
+        sgt = &attach->sgt;
+
+        /* release the scatterlist cache */
+        if (attach->dma_dir != DMA_NONE)
+                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+                        attach->dma_dir);
+        sg_free_table(sgt);
+        kfree(attach);
+        db_attach->priv = NULL;
+}
+
+static struct sg_table *vb2_dma_sg_dmabuf_ops_map(
+        struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
+{
+        struct vb2_dma_sg_attachment *attach = db_attach->priv;
+        /* stealing dmabuf mutex to serialize map/unmap operations */
+        struct mutex *lock = &db_attach->dmabuf->lock;
+        struct sg_table *sgt;
+        int ret;
+
+        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 */
+        ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dma_dir);
+        if (ret <= 0) {
+                pr_err("failed to map scatterlist\n");
+                mutex_unlock(lock);
+                return ERR_PTR(-EIO);
+        }
+
+        attach->dma_dir = dma_dir;
+
+        mutex_unlock(lock);
+
+        return sgt;
+}
+
+static void vb2_dma_sg_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
+        struct sg_table *sgt, enum dma_data_direction dma_dir)
+{
+        /* nothing to be done here */
+}
+
+static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
+{
+        /* drop reference obtained in vb2_dma_sg_get_dmabuf */
+        vb2_dma_sg_put(dbuf->priv);
+}
+
+static void *vb2_dma_sg_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
+{
+        struct vb2_dma_sg_buf *buf = dbuf->priv;
+
+        return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
+}
+
+static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
+{
+        struct vb2_dma_sg_buf *buf = dbuf->priv;
+
+        return vb2_dma_sg_vaddr(buf);
+}
+
+static int vb2_dma_sg_dmabuf_ops_mmap(struct dma_buf *dbuf,
+        struct vm_area_struct *vma)
+{
+        return vb2_dma_sg_mmap(dbuf->priv, vma);
+}
+
+static struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
+        .attach = vb2_dma_sg_dmabuf_ops_attach,
+        .detach = vb2_dma_sg_dmabuf_ops_detach,
+        .map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
+        .unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
+        .kmap = vb2_dma_sg_dmabuf_ops_kmap,
+        .kmap_atomic = vb2_dma_sg_dmabuf_ops_kmap,
+        .vmap = vb2_dma_sg_dmabuf_ops_vmap,
+        .mmap = vb2_dma_sg_dmabuf_ops_mmap,
+        .release = vb2_dma_sg_dmabuf_ops_release,
+};
+
+static struct dma_buf *vb2_dma_sg_get_dmabuf(void *buf_priv, unsigned long flags)
+{
+        struct vb2_dma_sg_buf *buf = buf_priv;
+        struct dma_buf *dbuf;
+
+        if (WARN_ON(!buf->dma_sgt))
+                return NULL;
+
+        dbuf = dma_buf_export(buf, &vb2_dma_sg_dmabuf_ops, buf->size, flags, NULL);
+        if (IS_ERR(dbuf))
+                return NULL;
+
+        /* dmabuf keeps reference to vb2 buffer */
+        atomic_inc(&buf->refcount);
+
+        return dbuf;
+}
+
+/*********************************************/
 /*       callbacks for DMABUF buffers        */
 /*********************************************/
 
@@ -523,6 +692,7 @@ const struct vb2_mem_ops vb2_dma_sg_memops = {
         .vaddr          = vb2_dma_sg_vaddr,
         .mmap           = vb2_dma_sg_mmap,
         .num_users      = vb2_dma_sg_num_users,
+        .get_dmabuf     = vb2_dma_sg_get_dmabuf,
         .map_dmabuf     = vb2_dma_sg_map_dmabuf,
         .unmap_dmabuf   = vb2_dma_sg_unmap_dmabuf,
         .attach_dmabuf  = vb2_dma_sg_attach_dmabuf,