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 <clew@codeaurora.org>
Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>

drivers/rpmsg/rpmsg_char.c

@@ -19,6 +19,7 @@
 #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>
 
@@ -76,6 +77,9 @@ struct rpmsg_eptdev {
 	spinlock_t queue_lock;
 	struct sk_buff_head queue;
 	wait_queue_head_t readq;
+
+	u32 rsigs;
+	bool sig_pending;
 };
 
 static int rpmsg_eptdev_destroy(struct device *dev, void *data)
@@ -120,6 +124,18 @@ static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void *buf, int len,
 	return 0;
 }
 
+static int rpmsg_sigs_cb(struct rpmsg_device *rpdev, void *priv, u32 sigs)
+{
+	struct rpmsg_eptdev *eptdev = priv;
+
+	eptdev->rsigs = sigs;
+	eptdev->sig_pending = true;
+
+	/* wake up any blocking processes, waiting for signal notification */
+	wake_up_interruptible(&eptdev->readq);
+	return 0;
+}
+
 static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 {
 	struct rpmsg_eptdev *eptdev = cdev_to_eptdev(inode->i_cdev);
@@ -139,6 +155,7 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
 		return -EINVAL;
 	}
 
+	ept->sig_cb = rpmsg_sigs_cb;
 	eptdev->ept = ept;
 	filp->private_data = eptdev;
 
@@ -157,6 +174,7 @@ static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
 		eptdev->ept = NULL;
 	}
 	mutex_unlock(&eptdev->ept_lock);
+	eptdev->sig_pending = false;
 
 	/* Discard all SKBs */
 	skb_queue_purge(&eptdev->queue);
@@ -267,6 +285,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
 	if (!skb_queue_empty(&eptdev->queue))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
+	if (eptdev->sig_pending)
+		mask |= EPOLLPRI;
+
 	mask |= rpmsg_poll(eptdev->ept, filp, wait);
 
 	return mask;
@@ -276,10 +297,32 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
 			       unsigned long arg)
 {
 	struct rpmsg_eptdev *eptdev = fp->private_data;
+	bool set;
+	u32 val;
+	int ret;
 
 	if (cmd != RPMSG_DESTROY_EPT_IOCTL)
 		return -EINVAL;
 
+	switch (cmd) {
+	case TIOCMGET:
+		eptdev->sig_pending = false;
+		ret = put_user(eptdev->rsigs, (int __user *)arg);
+		break;
+	case TIOCMSET:
+		ret = get_user(val, (int __user *)arg);
+		if (ret)
+			break;
+		set = (val & TIOCM_DTR) ? true : false;
+		ret = rpmsg_set_flow_control(eptdev->ept, set);
+		break;
+	case RPMSG_DESTROY_EPT_IOCTL:
+		ret = rpmsg_eptdev_destroy(&eptdev->dev, NULL);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
 	return rpmsg_eptdev_destroy(&eptdev->dev, NULL);
 }