[PATCH 02/13] rpmsg: introduce rpmsg_control driver for channel creation

[Arnaud Pouliquen <arnaud.pouliquen@st.com>]

Create a RPMsg driver that will offer to the userspace applications an
ioctl to manage channels.
As a first step, this driver just creates the /dev/rpmsg_ctl<x>
( <x> is the instance value). The ioctl is not implemented.

Notice that this driver is associated to a RPMsg device with no endpoint.
Instantiating this device as an RPMsg device allows to retrieve the
associated RPMsg backend.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
---
 drivers/rpmsg/Kconfig      |   8 ++
 drivers/rpmsg/Makefile     |   1 +
 drivers/rpmsg/rpmsg_ctrl.c | 209 +++++++++++++++++++++++++++++++++++++
 3 files changed, 218 insertions(+)
 create mode 100644 drivers/rpmsg/rpmsg_ctrl.c

diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
index 900ec8f54081..c5afbf24e793 100644
--- a/drivers/rpmsg/Kconfig
+++ b/drivers/rpmsg/Kconfig
@@ -23,6 +23,14 @@ config RPMSG_NS
 	  channel that probes the associate RPMsg device on remote endpoint
 	  service announcement.
 
+config RPMSG_CTRL
+	tristate "RPMSG control interface"
+	depends on RPMSG
+	help
+	  Say Y here to enable the support of the name service announcement
+	  channel that probe the associate RPMsg device on remote endpoint
+	  service announcement.
+
 config RPMSG_RAW
 	tristate "RPMSG raw service driver"
 	depends on RPMSG
diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
index d75f0a65e71d..dc5228022dac 100644
--- a/drivers/rpmsg/Makefile
+++ b/drivers/rpmsg/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_RPMSG)		+= rpmsg_core.o
 obj-$(CONFIG_RPMSG_CHAR)	+= rpmsg_char.o
 obj-$(CONFIG_RPMSG_NS)		+= rpmsg_ns.o
+obj-$(CONFIG_RPMSG_CTRL)	+= rpmsg_ctrl.o
 obj-$(CONFIG_RPMSG_MTK_SCP)	+= mtk_rpmsg.o
 qcom_glink-objs			:= qcom_glink_native.o qcom_glink_ssr.o
 obj-$(CONFIG_RPMSG_QCOM_GLINK) += qcom_glink.o
diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
new file mode 100644
index 000000000000..d31b1ba51fa7
--- /dev/null
+++ b/drivers/rpmsg/rpmsg_ctrl.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STMicroelectronics 2020
+ */
+#include <linux/cdev.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "rpmsg_internal.h"
+#include <uapi/linux/rpmsg.h>
+
+#define RPMSG_DEV_MAX	(MINORMASK + 1)
+
+#define dev_to_ctrldev(dev) container_of(dev, struct rpmsg_ctrl_dev, dev)
+#define cdev_to_ctrldev(i_cdev) container_of(i_cdev, struct rpmsg_ctrl_dev, cdev)
+
+/**
+ * struct rpmsg_ctrl_dev - control device for instantiating endpoint devices
+ * @rpdev:	underlaying rpmsg device
+ * @cdev:	cdev for the ctrl device
+ * @dev:	device for the ctrl device
+ */
+struct rpmsg_ctrl_dev {
+	struct rpmsg_device *rpdev;
+	struct cdev cdev;
+	struct device dev;
+};
+
+static DEFINE_IDA(rpmsg_ctrl_ida);
+static DEFINE_IDA(rpmsg_minor_ida);
+
+static dev_t rpmsg_major;
+
+static int rpmsg_ctrl_dev_open(struct inode *inode, struct file *filp)
+{
+	struct rpmsg_ctrl_dev *ctrldev = cdev_to_ctrldev(inode->i_cdev);
+
+	get_device(&ctrldev->dev);
+	filp->private_data = ctrldev;
+
+	return 0;
+}
+
+static long rpmsg_ctrl_dev_ioctl(struct file *fp, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct rpmsg_ctrl_dev *ctrldev = fp->private_data;
+
+	dev_info(&ctrldev->dev, "Control not yet implemented\n");
+
+	return 0;
+};
+
+static int rpmsg_ctrl_dev_release(struct inode *inode, struct file *filp)
+{
+	struct rpmsg_ctrl_dev *ctrldev = cdev_to_ctrldev(inode->i_cdev);
+
+	put_device(&ctrldev->dev);
+
+	return 0;
+}
+
+static void rpmsg_ctrl_dev_release_device(struct device *dev)
+{
+	struct rpmsg_ctrl_dev *ctrldev = dev_to_ctrldev(dev);
+
+	dev_err(dev, "%s\n", __func__);
+
+	ida_simple_remove(&rpmsg_ctrl_ida, dev->id);
+	ida_simple_remove(&rpmsg_minor_ida, MINOR(dev->devt));
+	cdev_del(&ctrldev->cdev);
+	kfree(ctrldev);
+}
+
+static const struct file_operations rpmsg_ctrl_fops = {
+	.owner = THIS_MODULE,
+	.open = rpmsg_ctrl_dev_open,
+	.release = rpmsg_ctrl_dev_release,
+	.unlocked_ioctl = rpmsg_ctrl_dev_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+};
+
+static int rpmsg_ctrl_add_control(struct rpmsg_ctrl_dev *ctrldev)
+{
+	struct device *dev = &ctrldev->dev;
+	int ret;
+
+	cdev_init(&ctrldev->cdev, &rpmsg_ctrl_fops);
+	ctrldev->cdev.owner = THIS_MODULE;
+
+	ret = ida_simple_get(&rpmsg_minor_ida, 0, RPMSG_DEV_MAX, GFP_KERNEL);
+	if (ret < 0)
+		return ret;
+	dev->devt = MKDEV(MAJOR(rpmsg_major), ret);
+
+	dev_set_name(dev, "rpmsg_ctrl%d", dev->id);
+
+	ret = cdev_add(&ctrldev->cdev, dev->devt, 1);
+	if (ret)
+		goto free_minor_ida;
+
+	dev_info(dev, "add %s control for %s driver\n",
+		 dev_name(dev),  dev_name(dev->parent));
+
+	return 0;
+
+free_minor_ida:
+	ida_simple_remove(&rpmsg_minor_ida, MINOR(dev->devt));
+
+	return ret;
+}
+
+static int rpmsg_ctrl_probe(struct rpmsg_device *rpdev)
+{
+	struct rpmsg_ctrl_dev *ctrldev;
+	struct device *dev;
+	int ret;
+
+	ctrldev = kzalloc(sizeof(*ctrldev), GFP_KERNEL);
+	if (!ctrldev)
+		return -ENOMEM;
+
+	ctrldev->rpdev = rpdev;
+
+	dev = &ctrldev->dev;
+	device_initialize(dev);
+	dev->parent = &rpdev->dev;
+
+	ret = ida_simple_get(&rpmsg_ctrl_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0)
+		goto free_ctrldev;
+
+	dev->id = ret;
+
+	ret = rpmsg_ctrl_add_control(ctrldev);
+	if (ret < 0)
+		goto free_ctrl_ida;
+
+	/* We can now rely on the release function for cleanup */
+	dev->release = rpmsg_ctrl_dev_release_device;
+
+	ret = device_add(dev);
+	if (ret) {
+		dev_err(&rpdev->dev, "device_add failed: %d\n", ret);
+		put_device(dev);
+		goto free_ctrl_ida;
+	}
+
+	dev_set_drvdata(dev, ctrldev);
+	dev_set_drvdata(&rpdev->dev, ctrldev);
+
+	return 0;
+
+free_ctrl_ida:
+	ida_simple_remove(&rpmsg_ctrl_ida, dev->id);
+free_ctrldev:
+	put_device(dev);
+	kfree(ctrldev);
+
+	return ret;
+}
+
+static void rpmsg_ctrl_remove(struct rpmsg_device *rpdev)
+{
+	struct rpmsg_ctrl_dev *ctrldev = dev_get_drvdata(&rpdev->dev);
+
+	device_del(&ctrldev->dev);
+	put_device(&ctrldev->dev);
+}
+
+static struct rpmsg_driver rpmsg_ctrl_driver = {
+	.probe = rpmsg_ctrl_probe,
+	.remove = rpmsg_ctrl_remove,
+	.drv = {
+		.name = "rpmsg_ctrl",
+	},
+};
+
+static int rpmsg_ctrl_init(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg");
+	if (ret < 0) {
+		pr_err("rpmsg: failed to allocate char dev region\n");
+		return ret;
+	}
+
+	ret = register_rpmsg_driver(&rpmsg_ctrl_driver);
+	if (ret < 0) {
+		pr_err("rpmsgchr: failed to register rpmsg driver\n");
+		unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
+	}
+
+	return ret;
+}
+postcore_initcall(rpmsg_ctrl_init);
+
+static void rpmsg_ctrl_exit(void)
+{
+	unregister_rpmsg_driver(&rpmsg_ctrl_driver);
+	unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
+}
+module_exit(rpmsg_ctrl_exit);
+
+MODULE_DESCRIPTION("Ioctl rpmsg driver");
+MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
+MODULE_ALIAS("rpmsg_ctl");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1