[RFC PATCH v1 2/2] dma-buf: add lock callback for fcntl system call.

[Inki Dae]

This patch adds lock callback to dma buf file operations,
and this callback will be called by fcntl system call.

With this patch, fcntl system call can be used for buffer
synchronization between CPU and CPU, and CPU and DMA in user mode.

Signed-off-by: Inki Dae <inki.dae at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
---
 drivers/base/dma-buf.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index fe39120..cd71447 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -31,6 +31,7 @@
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/reservation.h>
+#include <linux/dmabuf-sync.h>
 
 static inline int is_dma_buf_file(struct file *);
 
@@ -82,9 +83,42 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 	return dmabuf->ops->mmap(dmabuf, vma);
 }
 
+static int dma_buf_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct dma_buf *dmabuf;
+	unsigned int type;
+	bool wait = false;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	if ((fl->fl_type & F_UNLCK) == F_UNLCK) {
+		dmabuf_sync_single_unlock(dmabuf);
+		return 0;
+	}
+
+	/* convert flock type to dmabuf sync type. */
+	if ((fl->fl_type & F_WRLCK) == F_WRLCK)
+		type = DMA_BUF_ACCESS_W;
+	else if ((fl->fl_type & F_RDLCK) == F_RDLCK)
+		type = DMA_BUF_ACCESS_R;
+	else
+		return -EINVAL;
+
+	if (fl->fl_flags & FL_SLEEP)
+		wait = true;
+
+	/* TODO. the locking to certain region should also be considered. */
+
+	return dmabuf_sync_single_lock(dmabuf, type, wait);
+}
+
 static const struct file_operations dma_buf_fops = {
 	.release	= dma_buf_release,
 	.mmap		= dma_buf_mmap_internal,
+	.lock		= dma_buf_lock,
 };
 
 /*
-- 
1.7.5.4