[PATCH 4/5] rpmsg: wakeup poll to notify signal update

[Arun Kumar Neelakantam]

Add support to wait on poll to get signal notifications.
Send POLLPRI mask to indicate the signal change.

Signed-off-by: Arun Kumar Neelakantam <ane...@codeaurora.org>
---
 drivers/rpmsg/rpmsg_char.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index c983d6c..aee5561 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;
+
+       atomic_t sig_pending;
 };
 
 static int rpmsg_eptdev_destroy(struct device *dev, void *data)
@@ -125,6 +128,12 @@ static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void 
*buf, int len,
 static int rpmsg_sigs_cb(struct rpmsg_device *rpdev, void *priv,
                         u32 old, u32 new)
 {
+       struct rpmsg_eptdev *eptdev = priv;
+
+       atomic_set(&eptdev->sig_pending, 1);
+
+       /* wake up any blocking processes, waiting for signal notification */
+       wake_up_interruptible(&eptdev->readq);
        return 0;
 }
 
@@ -164,6 +173,7 @@ static int rpmsg_eptdev_release(struct inode *inode, struct 
file *filp)
                eptdev->ept = NULL;
        }
        mutex_unlock(&eptdev->ept_lock);
+       atomic_set(&eptdev->sig_pending, 0);
 
        /* Discard all SKBs */
        while (!skb_queue_empty(&eptdev->queue)) {
@@ -270,6 +280,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, 
poll_table *wait)
        if (!skb_queue_empty(&eptdev->queue))
                mask |= EPOLLIN | EPOLLRDNORM;
 
+       if (atomic_read(&eptdev->sig_pending))
+               mask |= POLLPRI;
+
        mask |= rpmsg_poll(eptdev->ept, filp, wait);
 
        return mask;
@@ -318,6 +331,7 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned 
int cmd,
                ret = rpmsg_get_sigs(eptdev->ept, &lsigs, &rsigs);
                if (!ret)
                        ret = put_user(rsigs, (u32 *)arg);
+               atomic_set(&eptdev->sig_pending, 0);
                break;
        case TIOCMSET:
        case TIOCMBIS:
-- 
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