rpmsg: qcom_smd: Implement endpoint "poll"

Add support for polling the status of the write buffer so that user
space can use rpmsg character devices in non-blocking mode.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/qcom_smd.c

@@ -919,6 +919,21 @@ static int qcom_smd_trysend(struct rpmsg_endpoint *ept, void *data, int len)
  return __qcom_smd_send(qsept->qsch, data, len, false);
 }
 
+static unsigned int qcom_smd_poll(struct rpmsg_endpoint *ept,
+ struct file *filp, poll_table *wait)
+{
+ struct qcom_smd_endpoint *qsept = to_smd_endpoint(ept);
+ struct qcom_smd_channel *channel = qsept->qsch;
+ unsigned int mask = 0;
+
+ poll_wait(filp, &channel->fblockread_event, wait);
+
+ if (qcom_smd_get_tx_avail(channel) > 20)
+ mask |= POLLOUT | POLLWRNORM;
+
+ return mask;
+}
+
 /*
  * Finds the device_node for the smd child interested in this channel.
  */
@@ -951,6 +966,7 @@ static const struct rpmsg_endpoint_ops qcom_smd_endpoint_ops = {
  .destroy_ept = qcom_smd_destroy_ept,
  .send = qcom_smd_send,
  .trysend = qcom_smd_trysend,
+ .poll = qcom_smd_poll,
 };
 
 /*