fpga: dfl: support multiple opens on feature device node.

Each DFL functional block, e.g. AFU (Accelerated Function Unit) and FME
(FPGA Management Engine), could implement more than one function within
its region, but current driver only allows one user application to access
it by exclusive open on device node. So this is not convenient and
flexible for userspace applications, as they have to combine lots of
different functions into one single application.

This patch removes the limitation here to allow multiple opens to each
feature device node for AFU and FME from userspace applications. If user
still needs exclusive access to these device node, O_EXCL flag must be
issued together with open.

Signed-off-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

1 files changed, 12 insertions, 7 deletions

diff --git a/drivers/fpga/dfl-fme-main.c b/drivers/fpga/dfl-fme-main.c
index 1d4690c99268..56d720c1af39 100644
--- a/drivers/fpga/dfl-fme-main.c
+++ b/drivers/fpga/dfl-fme-main.c
@@ -600,14 +600,16 @@ static int fme_open(struct inode *inode, struct file *filp)
 	if (WARN_ON(!pdata))
 		return -ENODEV;
 
-	ret = dfl_feature_dev_use_begin(pdata);
-	if (ret)
-		return ret;
-
-	dev_dbg(&fdev->dev, "Device File Open\n");
-	filp->private_data = pdata;
+	mutex_lock(&pdata->lock);
+	ret = dfl_feature_dev_use_begin(pdata, filp->f_flags & O_EXCL);
+	if (!ret) {
+		dev_dbg(&fdev->dev, "Device File Opened %d Times\n",
+			dfl_feature_dev_use_count(pdata));
+		filp->private_data = pdata;
+	}
+	mutex_unlock(&pdata->lock);
 
-	return 0;
+	return ret;
 }
 
 static int fme_release(struct inode *inode, struct file *filp)
@@ -616,7 +618,10 @@ static int fme_release(struct inode *inode, struct file *filp)
 	struct platform_device *pdev = pdata->dev;
 
 	dev_dbg(&pdev->dev, "Device File Release\n");
+
+	mutex_lock(&pdata->lock);
 	dfl_feature_dev_use_end(pdata);
+	mutex_unlock(&pdata->lock);
 
 	return 0;
 }