[PATCH V3 4/4] rpmsg: char: Add signal callback and POLLPRI support

[Arun Kumar Neelakantam]

Register a callback to get the signal notifications from rpmsg and
send POLLPRI mask to indicate the signal change in POLL system call.

Signed-off-by: Arun Kumar Neelakantam <ane...@codeaurora.org>
---
 drivers/rpmsg/rpmsg_char.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 16978f7b..a5855f7 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -64,6 +64,7 @@ struct rpmsg_ctrldev {
  * @queue_lock:        synchronization of @queue operations
  * @queue:     incoming message queue
  * @readq:     wait object for incoming queue
+ * @sig_pending:state of signal notification
  */
 struct rpmsg_eptdev {
        struct device dev;
@@ -78,6 +79,8 @@ struct rpmsg_eptdev {
        spinlock_t queue_lock;
        struct sk_buff_head queue;
        wait_queue_head_t readq;
+
+       bool sig_pending;
 };
 
 static int rpmsg_eptdev_destroy(struct device *dev, void *data)
@@ -122,6 +125,18 @@ 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 old, u32 new)
+{
+       struct rpmsg_eptdev *eptdev = priv;
+
+       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);
@@ -138,6 +153,7 @@ 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 +173,7 @@ 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 */
        while (!skb_queue_empty(&eptdev->queue)) {
@@ -263,6 +280,9 @@ 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 |= POLLPRI;
+
        mask |= rpmsg_poll(eptdev->ept, filp, wait);
 
        return mask;
@@ -306,6 +326,7 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned 
int cmd,
 
        switch (cmd) {
        case TIOCMGET:
+               eptdev->sig_pending = false;
                ret = rpmsg_get_signals(eptdev->ept);
                if (!ret)
                        ret = put_user(ret, (int __user *)arg);
-- 
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