Re: [PATCH v2 01/16] rpmsg: introduce RPMsg control driver for channel creation

Mathieu Poirier
2021-01-21T23:32:32Z

Hi Arnaud,

On Tue, Dec 22, 2020 at 11:57:11AM +0100, Arnaud Pouliquen wrote:
> The RPMsg_ctrl driver is a duplication of the ioctrl part of the
> rpmsg_char driver to make generic the ioctl to manage channels by
> the userspace applications.
>
> 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@foss.st.com>
> ---
> drivers/rpmsg/Kconfig | 8 ++
> drivers/rpmsg/Makefile | 1 +
> drivers/rpmsg/rpmsg_ctrl.c | 208 +++++++++++++++++++++++++++++++++++++
> 3 files changed, 217 insertions(+)
> create mode 100644 drivers/rpmsg/rpmsg_ctrl.c
>
> diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
> index 0b4407abdf13..c9e602016c3b 100644
> --- a/drivers/rpmsg/Kconfig
> +++ b/drivers/rpmsg/Kconfig
> @@ -23,6 +23,14 @@ config RPMSG_NS
> channel that probes the associated 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 /dev/rpmsg_ctl API. this API
> + allows user-space programs to create channels with specific name,
> + source and destination addresses.
> +
> config RPMSG_MTK_SCP
> tristate "MediaTek SCP"
> depends on MTK_SCP
> diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
> index 8d452656f0ee..3c1bce9d0228 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..425c3e32ada4
> --- /dev/null
> +++ b/drivers/rpmsg/rpmsg_ctrl.c
> @@ -0,0 +1,208 @@
> +// 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;
> +};

As Bjorn pointed out it would be better modify rpmsg_char.c to what you want it
to be rather than spinning off a parallel implementation. One immediate
advantage would be to avoid the creation of new structures that are identical to
existing ones. There's also the problem of bisecting... If I remember
correctly there are a few instances where applying this set would break a bisect
session.

> +
> +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__);

Debug left over.

> +
> + 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);

Here "rpmsg_ctrl" is used but the changelog and refers to "rpmsg_ctl". Using
the latter would, as Bjorn pointed out, break existing implementation.

> +
> + 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 = {
> + .drv.name = KBUILD_MODNAME,
> + .probe = rpmsg_ctrl_probe,
> + .remove = rpmsg_ctrl_remove,
> +};
> +
> +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_ctrl: failed to allocate char dev region\n");
> + return ret;
> + }
> +
> + ret = register_rpmsg_driver(&rpmsg_ctrl_driver);
> + if (ret < 0) {
> + pr_err("rpmsg_ctrl: 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:" KBUILD_MODNAME);
> +MODULE_LICENSE("GPL v2");
> --
> 2.17.1
>