linux-kernel - [PATCH v2 03/15] media: videobuf2: Allow exporting of a struct dmabuf

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Message-ID: <20231109210309.638594-4-umang.jain@ideasonboard.com>
Date:   Thu,  9 Nov 2023 16:02:55 -0500
From:   Umang Jain <umang.jain@...asonboard.com>
To:     linux-media@...r.kernel.org, kernel-list@...pberrypi.com,
        linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-staging@...ts.linux.dev
Cc:     Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        "Ricardo B . Marliere" <ricardo@...liere.net>,
        Dan Carpenter <error27@...il.com>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.org>,
        Umang Jain <umang.jain@...asonboard.com>
Subject: [PATCH v2 03/15] media: videobuf2: Allow exporting of a struct dmabuf

From: Dave Stevenson <dave.stevenson@...pberrypi.org>

videobuf2 only allowed exporting a dmabuf as a file descriptor,
but there are instances where having the struct dma_buf is
useful within the kernel.

Split the current implementation into two, one step which
exports a struct dma_buf, and the second which converts that
into an fd.

Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.org>
Signed-off-by: Umang Jain <umang.jain@...asonboard.com>
---
 .../media/common/videobuf2/videobuf2-core.c   | 36 +++++++++++++------
 include/media/videobuf2-core.h                | 15 ++++++++
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 27aee92f3eea..8ba85c2db375 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -2229,49 +2229,49 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
 	return -EINVAL;
 }
 
-int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
-		unsigned int index, unsigned int plane, unsigned int flags)
+struct dma_buf *vb2_core_expbuf_dmabuf(struct vb2_queue *q, unsigned int type,
+				       unsigned int index, unsigned int plane,
+				       unsigned int flags)
 {
 	struct vb2_buffer *vb = NULL;
 	struct vb2_plane *vb_plane;
-	int ret;
 	struct dma_buf *dbuf;
 
 	if (q->memory != VB2_MEMORY_MMAP) {
 		dprintk(q, 1, "queue is not currently set up for mmap\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (!q->mem_ops->get_dmabuf) {
 		dprintk(q, 1, "queue does not support DMA buffer exporting\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (flags & ~(O_CLOEXEC | O_ACCMODE)) {
 		dprintk(q, 1, "queue does support only O_CLOEXEC and access mode flags\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (type != q->type) {
 		dprintk(q, 1, "invalid buffer type\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (index >= q->num_buffers) {
 		dprintk(q, 1, "buffer index out of range\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	vb = q->bufs[index];
 
 	if (plane >= vb->num_planes) {
 		dprintk(q, 1, "buffer plane out of range\n");
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (vb2_fileio_is_active(q)) {
 		dprintk(q, 1, "expbuf: file io in progress\n");
-		return -EBUSY;
+		return ERR_PTR(-EBUSY);
 	}
 
 	vb_plane = &vb->planes[plane];
@@ -2283,9 +2283,23 @@ int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
 	if (IS_ERR_OR_NULL(dbuf)) {
 		dprintk(q, 1, "failed to export buffer %d, plane %d\n",
 			index, plane);
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 	}
 
+	return dbuf;
+}
+EXPORT_SYMBOL_GPL(vb2_core_expbuf_dmabuf);
+
+int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
+		    unsigned int index, unsigned int plane, unsigned int flags)
+{
+	struct dma_buf *dbuf;
+	int ret;
+
+	dbuf = vb2_core_expbuf_dmabuf(q, type, index, plane, flags);
+	if (IS_ERR(dbuf))
+		return PTR_ERR(dbuf);
+
 	ret = dma_buf_fd(dbuf, flags & ~O_ACCMODE);
 	if (ret < 0) {
 		dprintk(q, 3, "buffer %d, plane %d failed to export (%d)\n",
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 4b6a9d2ea372..cba4e495f6a2 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -925,6 +925,21 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type);
  */
 int vb2_core_streamoff(struct vb2_queue *q, unsigned int type);
 
+/**
+ * vb2_core_expbuf_dmabuf() - Export a buffer as a dma_buf structure
+ * @q:         videobuf2 queue
+ * @type:      buffer type
+ * @index:     id number of the buffer
+ * @plane:     index of the plane to be exported, 0 for single plane queues
+ * @flags:     flags for newly created file, currently only O_CLOEXEC is
+ *             supported, refer to manual of open syscall for more details
+ *
+ * Return: Returns the dmabuf pointer
+ */
+struct dma_buf *vb2_core_expbuf_dmabuf(struct vb2_queue *q, unsigned int type,
+				       unsigned int index, unsigned int plane,
+				       unsigned int flags);
+
 /**
  * vb2_core_expbuf() - Export a buffer as a file descriptor.
  * @q:		pointer to &struct vb2_queue with videobuf2 queue.
-- 
2.41.0