[RFCv2 PATCH 6/9] v4l: vb2-dma-contig: add support for DMABUF exporting

[Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>]

This patch adds support for exporting a dma-contig buffer using
DMABUF interface.

Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
 drivers/media/video/videobuf2-dma-contig.c |  128 ++++++++++++++++++++++++++++
 1 files changed, 128 insertions(+), 0 deletions(-)

diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c
index 746dd5f..d95b23a 100644
--- a/drivers/media/video/videobuf2-dma-contig.c
+++ b/drivers/media/video/videobuf2-dma-contig.c
@@ -31,6 +31,7 @@ struct vb2_dc_buf {
 	/* MMAP related */
 	struct vb2_vmarea_handler	handler;
 	atomic_t			refcount;
+	struct dma_buf			*dma_buf;
 	struct sg_table			*sgt_base;
 
 	/* USERPTR related */
@@ -194,6 +195,8 @@ static void vb2_dc_put(void *buf_priv)
 	if (!atomic_dec_and_test(&buf->refcount))
 		return;
 
+	if (buf->dma_buf)
+		dma_buf_put(buf->dma_buf);
 	vb2_dc_release_sgtable(buf->sgt_base);
 	dma_free_coherent(buf->dev, buf->size, buf->vaddr,
 		buf->dma_addr);
@@ -309,6 +312,130 @@ static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
 }
 
 /*********************************************/
+/*         DMABUF ops for exporters          */
+/*********************************************/
+
+struct vb2_dc_attachment {
+	struct sg_table sgt;
+	enum dma_data_direction dir;
+};
+
+static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
+	struct dma_buf_attachment *dbuf_attach)
+{
+	/* nothing to be done */
+	return 0;
+}
+
+static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
+	struct dma_buf_attachment *db_attach)
+{
+	struct vb2_dc_attachment *attach = db_attach->priv;
+	struct sg_table *sgt;
+
+	if (!attach)
+		return;
+
+	sgt = &attach->sgt;
+
+	dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->nents, attach->dir);
+	sg_free_table(sgt);
+	kfree(attach);
+	db_attach->priv = NULL;
+}
+
+static struct sg_table *vb2_dc_dmabuf_ops_map(
+	struct dma_buf_attachment *db_attach, enum dma_data_direction dir)
+{
+	struct dma_buf *dbuf = db_attach->dmabuf;
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct vb2_dc_attachment *attach = db_attach->priv;
+	struct sg_table *sgt;
+	struct scatterlist *rd, *wr;
+	int i, ret;
+
+	/* return previously mapped sg table */
+	if (attach)
+		return &attach->sgt;
+
+	attach = kzalloc(sizeof *attach, GFP_KERNEL);
+	if (!attach)
+		return ERR_PTR(-ENOMEM);
+
+	sgt = &attach->sgt;
+	attach->dir = dir;
+
+	/* copying the buf->base_sgt to attachment */
+	ret = sg_alloc_table(sgt, buf->sgt_base->orig_nents, GFP_KERNEL);
+	if (ret) {
+		kfree(attach);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	rd = buf->sgt_base->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);
+	}
+
+	/* mapping new sglist to the client */
+	ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dir);
+	if (ret <= 0) {
+		printk(KERN_ERR "failed to map scatterlist\n");
+		sg_free_table(sgt);
+		kfree(attach);
+		return ERR_PTR(-EIO);
+	}
+
+	db_attach->priv = attach;
+
+	return sgt;
+}
+
+static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
+	struct sg_table *sgt)
+{
+	/* nothing to be done here */
+}
+
+static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
+{
+	/* drop reference obtained in vb2_dc_get_dmabuf */
+	vb2_dc_put(dbuf->priv);
+}
+
+static struct dma_buf_ops vb2_dc_dmabuf_ops = {
+	.attach = vb2_dc_dmabuf_ops_attach,
+	.detach = vb2_dc_dmabuf_ops_detach,
+	.map_dma_buf = vb2_dc_dmabuf_ops_map,
+	.unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
+	.release = vb2_dc_dmabuf_ops_release,
+};
+
+static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	struct dma_buf *dbuf;
+
+	if (buf->dma_buf)
+		return buf->dma_buf;
+
+	/* dmabuf keeps reference to vb2 buffer */
+	atomic_inc(&buf->refcount);
+	dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, 0);
+	if (IS_ERR(dbuf)) {
+		atomic_dec(&buf->refcount);
+		return NULL;
+	}
+
+	buf->dma_buf = dbuf;
+
+	return dbuf;
+}
+
+/*********************************************/
 /*       callbacks for USERPTR buffers       */
 /*********************************************/
 
@@ -603,6 +730,7 @@ static void *vb2_dc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf,
 const struct vb2_mem_ops vb2_dma_contig_memops = {
 	.alloc		= vb2_dc_alloc,
 	.put		= vb2_dc_put,
+	.get_dmabuf	= vb2_dc_get_dmabuf,
 	.cookie		= vb2_dc_cookie,
 	.vaddr		= vb2_dc_vaddr,
 	.mmap		= vb2_dc_mmap,
-- 
1.7.5.4

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