linux-kernel - [RFC PATCH 04/10] rpmsg: virtio: Implement the announce_remote

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Date:   Fri, 20 May 2022 10:29:34 +0200
From:   Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        Deepak Kumar Singh <quic_deesin@...cinc.com>,
        Chris Lew <quic_clew@...cinc.com>,
        <arnaud.pouliquen@...s.st.com>
Subject: [RFC PATCH 04/10] rpmsg: virtio: Implement the announce_remote_fc ops

Add the capability for a rpmsg local endpoint to receive information
of a remote endpoint state using the flow control channel.

The virtio_rpmsg_remote_flowctrl function calls the endpoint which
matches with the chinfo.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
---
 drivers/rpmsg/virtio_rpmsg_bus.c | 38 ++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 0db8043e6c49..785fda77984e 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -305,6 +305,7 @@ __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
 	/* make sure in-flight inbound messages won't invoke cb anymore */
 	mutex_lock(&ept->cb_lock);
 	ept->cb = NULL;
+	ept->sig_cb =  NULL;
 	mutex_unlock(&ept->cb_lock);
 
 	kref_put(&ept->refcount, __ept_release);
@@ -365,12 +366,49 @@ static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
 	return err;
 }
 
+static int virtio_rpmsg_remote_flowctrl(struct rpmsg_device *rpdev,
+					struct rpmsg_channel_info *chinfo,
+					bool enable)
+{
+	struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
+	struct virtproc_info *vrp = vch->vrp;
+	struct rpmsg_endpoint *ept;
+
+	/* Use the dst addr to fetch the callback of the appropriate user */
+	mutex_lock(&vrp->endpoints_lock);
+
+	ept = idr_find(&vrp->endpoints, chinfo->dst);
+
+	/* Let's make sure no one deallocates ept while we use it */
+	if (ept)
+		kref_get(&ept->refcount);
+
+	mutex_unlock(&vrp->endpoints_lock);
+
+	if (!ept)
+		return -EINVAL;
+
+	/* Make sure ept->sig_cb doesn't go away while we use it */
+	mutex_lock(&ept->cb_lock);
+
+	if (ept->sig_cb)
+		ept->sig_cb(ept->rpdev, ept->priv, enable);
+
+	mutex_unlock(&ept->cb_lock);
+
+	/* Farewell, ept, we don't need you anymore */
+	kref_put(&ept->refcount, __ept_release);
+
+	return 0;
+}
+
 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
 	.create_channel = virtio_rpmsg_create_channel,
 	.release_channel = virtio_rpmsg_release_channel,
 	.create_ept = virtio_rpmsg_create_ept,
 	.announce_create = virtio_rpmsg_announce_create,
 	.announce_destroy = virtio_rpmsg_announce_destroy,
+	.announce_remote_fc = virtio_rpmsg_remote_flowctrl,
 };
 
 static void virtio_rpmsg_release_device(struct device *dev)
-- 
2.25.1