linux-kernel - [PATCH v5 16/16] rpmsg: char: return an error if device already open

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Date:   Fri, 19 Feb 2021 12:15:01 +0100
From:   Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Andy Gross <agross@...nel.org>
CC:     <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-msm@...r.kernel.org>, <arnaud.pouliquen@...s.st.com>
Subject: [PATCH v5 16/16] rpmsg: char: return an error if device already open

The rpmsg_create_ept function is invoked when the device is opened.
As only one endpoint must be created per device. It is not possible to
open the same device twice. But there is nothing to prevent multi open.
Return -EBUSY when device is already opened to have a generic error
instead of relying on the back-end to potentially detect the error.

Without this patch for instance the GLINK driver return -EBUSY while
the virtio bus return -ENOSPC.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
---
 drivers/rpmsg/rpmsg_char.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 8d3f9d6c20ad..4cd5b79559f0 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -116,6 +116,9 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 	struct device *dev = &eptdev->dev;
 	u32 addr = eptdev->chinfo.src;
 
+	if (eptdev->ept)
+		return -EBUSY;
+
 	get_device(dev);
 
 	/*
-- 
2.17.1