linux-kernel - [PATCH V4 3/3] rpmsg: char: Add TIOCMGET/TIOCMSET ioctl support

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Date:   Wed, 7 Dec 2022 18:34:18 +0530
From:   Sarannya S <quic_sarannya@...cinc.com>
To:     <quic_bjorande@...cinc.com>, <arnaud.pouliquen@...s.st.com>,
        <swboyd@...omium.org>, <quic_clew@...cinc.com>,
        <mathieu.poirier@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        Sarannya S <quic_sarannya@...cinc.com>,
        Deepak Kumar Singh <quic_deesin@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>
Subject: [PATCH V4 3/3] rpmsg: char: Add TIOCMGET/TIOCMSET ioctl support

Add TICOMGET and TIOCMSET ioctl support for rpmsg char device nodes
to get/set the low level transport signals.

Signed-off-by: Chris Lew <quic_clew@...cinc.com>
Signed-off-by: Deepak Kumar Singh <quic_deesin@...cinc.com>
Signed-off-by: Sarannya S <quic_sarannya@...cinc.com>
---
 drivers/rpmsg/rpmsg_char.c | 60 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 52 insertions(+), 8 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 3e0b8f3..8109d18 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -23,6 +23,7 @@
 #include <linux/rpmsg.h>
 #include <linux/skbuff.h>
 #include <linux/slab.h>
+#include <linux/termios.h>
 #include <linux/uaccess.h>
 #include <uapi/linux/rpmsg.h>
 
@@ -68,6 +69,8 @@ struct rpmsg_eptdev {
 	struct sk_buff_head queue;
 	wait_queue_head_t readq;
 
+	u32 remote_signals;
+	bool signals_pending;
 };
 
 int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
@@ -109,7 +112,22 @@ static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void *buf, int len,
 	skb_queue_tail(&eptdev->queue, skb);
 	spin_unlock(&eptdev->queue_lock);
 
-	/* wake up any blocking processes, waiting for new data */
+	wake_up_interruptible(&eptdev->readq);
+
+	return 0;
+}
+
+static int rpmsg_ept_flow_cb(struct rpmsg_device *rpdev, void *priv, bool enable)
+{
+	struct rpmsg_eptdev *eptdev = priv;
+
+	if (enable)
+		eptdev->remote_signals = TIOCM_DSR | TIOCM_CTS;
+	else
+		eptdev->remote_signals = 0;
+
+	eptdev->signals_pending = true;
+
 	wake_up_interruptible(&eptdev->readq);
 
 	return 0;
@@ -146,6 +164,7 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 		return -EINVAL;
 	}
 
+	ept->flow_cb = rpmsg_ept_flow_cb;
 	eptdev->ept = ept;
 	filp->private_data = eptdev;
 	mutex_unlock(&eptdev->ept_lock);
@@ -166,6 +185,7 @@ static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
 		eptdev->ept = NULL;
 	}
 	mutex_unlock(&eptdev->ept_lock);
+	eptdev->signals_pending = false;
 
 	/* Discard all SKBs */
 	skb_queue_purge(&eptdev->queue);
@@ -279,6 +299,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
 	if (!skb_queue_empty(&eptdev->queue))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
+	if (eptdev->signals_pending)
+		mask |= EPOLLPRI;
+
 	mask |= rpmsg_poll(eptdev->ept, filp, wait);
 
 	return mask;
@@ -289,14 +312,35 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
 {
 	struct rpmsg_eptdev *eptdev = fp->private_data;
 
-	if (cmd != RPMSG_DESTROY_EPT_IOCTL)
-		return -EINVAL;
-
-	/* Don't allow to destroy a default endpoint. */
-	if (eptdev->default_ept)
-		return -EINVAL;
+	bool set;
+	u32 val;
+	int ret;
+	
+	switch (cmd) {
+	case TIOCMGET:
+		eptdev->signals_pending = false;
+		ret = put_user(eptdev->remote_signals, (int __user *)arg);
+		break;
+	case TIOCMSET:
+		ret = get_user(val, (int __user *)arg);
+		if (ret)
+			break;
+		set = (val & (TIOCM_DTR | TIOCM_RTS)) ? true : false;
+		ret = rpmsg_set_flow_control(eptdev->ept, set, 0);
+		break;
+	case RPMSG_DESTROY_EPT_IOCTL:
+		/* Don't allow to destroy a default endpoint. */
+		if (eptdev->default_ept) {
+			ret = -EINVAL;
+			break;
+		}
+		ret = rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
+		break;
+	default:
+		ret = -EINVAL;
+	}
 
-	return rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
+	return ret;
 }
 
 static const struct file_operations rpmsg_eptdev_fops = {
-- 
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