linux-kernel - [PATCH v2 5/7] rpmsg: char: Introduce a rpmsg driver for the rpmsg char device

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Date:   Tue, 13 Apr 2021 15:44:56 +0200
From:   Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <arnaud.pouliquen@...s.st.com>
Subject: [PATCH v2 5/7] rpmsg: char: Introduce a rpmsg driver for the rpmsg char device

A rpmsg char device allows to probe the endpoint device on a remote name
service announcement.

With this patch the /dev/rpmsgX interface is created either by a user
application or by the remote firmware.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>

---
update from V1:
 - add missing unregister_rpmsg_driver call on module exit.

---
 drivers/rpmsg/rpmsg_char.c | 59 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index a64249d83172..4606787b7011 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -26,6 +26,8 @@
 #include "rpmsg_char.h"
 #include "rpmsg_internal.h"
 
+#define RPMSG_CHAR_DEVNAME "rpmsg-raw"
+
 static dev_t rpmsg_major;
 
 static DEFINE_IDA(rpmsg_ept_ida);
@@ -403,13 +405,67 @@ int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent
 }
 EXPORT_SYMBOL(rpmsg_chrdev_create_eptdev);
 
+static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
+{
+	struct rpmsg_channel_info chinfo;
+	struct rpmsg_eptdev *eptdev;
+
+	if (!rpdev->ept)
+		return -EINVAL;
+
+	memcpy(chinfo.name, RPMSG_CHAR_DEVNAME, sizeof(RPMSG_CHAR_DEVNAME));
+	chinfo.src = rpdev->src;
+	chinfo.dst = rpdev->dst;
+
+	eptdev = __rpmsg_chrdev_create_eptdev(rpdev, &rpdev->dev, chinfo, NULL);
+	if (IS_ERR(eptdev))
+		return PTR_ERR(eptdev);
+
+	/* Set the private field of the default endpoint to retrieve context on callback. */
+	rpdev->ept->priv = eptdev;
+
+	return 0;
+}
+
+static void rpmsg_chrdev_remove(struct rpmsg_device *rpdev)
+{
+	int ret;
+
+	ret = device_for_each_child(&rpdev->dev, NULL, rpmsg_chrdev_destroy_eptdev);
+	if (ret)
+		dev_warn(&rpdev->dev, "failed to destroy endpoints: %d\n", ret);
+}
+
+static struct rpmsg_device_id rpmsg_chrdev_id_table[] = {
+	{ .name	= RPMSG_CHAR_DEVNAME },
+	{ },
+};
+
+static struct rpmsg_driver rpmsg_chrdev_driver = {
+	.probe = rpmsg_chrdev_probe,
+	.remove = rpmsg_chrdev_remove,
+	.id_table = rpmsg_chrdev_id_table,
+	.callback = rpmsg_ept_cb,
+	.drv = {
+		.name = "rpmsg_chrdev",
+	},
+};
+
 static int rpmsg_chrdev_init(void)
 {
 	int ret;
 
 	ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg_char");
-	if (ret < 0)
+	if (ret < 0) {
 		pr_err("rpmsg: failed to allocate char dev region\n");
+		return ret;
+	}
+
+	ret = register_rpmsg_driver(&rpmsg_chrdev_driver);
+	if (ret < 0) {
+		pr_err("rpmsg: failed to register rpmsg raw driver\n");
+		unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
+	}
 
 	return ret;
 }
@@ -417,6 +473,7 @@ postcore_initcall(rpmsg_chrdev_init);
 
 static void rpmsg_chrdev_exit(void)
 {
+	unregister_rpmsg_driver(&rpmsg_chrdev_driver);
 	unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
 }
 module_exit(rpmsg_chrdev_exit);
-- 
2.17.1