Re: [PATCH v3 1/2] remoteproc: Add remoteproc character device interface

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Tue, Apr 21, 2020 at 11:10:17AM -0700, Rishabh Bhatnagar wrote:
> Add the character device interface into remoteproc framework.
> This interface can be used in order to boot/shutdown remote
> subsystems and provides a basic ioctl based interface to implement
> supplementary functionality. An ioctl call is implemented to enable
> the shutdown on release feature which will allow remote processors to
> be shutdown when the controlling userpsace application crashes or hangs.
> 
> Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> ---
>  Documentation/userspace-api/ioctl/ioctl-number.rst |   1 +
>  drivers/remoteproc/Kconfig                         |   9 ++
>  drivers/remoteproc/Makefile                        |   1 +
>  drivers/remoteproc/remoteproc_cdev.c               | 143 +++++++++++++++++++++
>  drivers/remoteproc/remoteproc_internal.h           |  21 +++
>  include/linux/remoteproc.h                         |   3 +
>  include/uapi/linux/remoteproc_cdev.h               |  20 +++
>  7 files changed, 198 insertions(+)
>  create mode 100644 drivers/remoteproc/remoteproc_cdev.c
>  create mode 100644 include/uapi/linux/remoteproc_cdev.h
> 
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 2e91370..412b2a0 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -337,6 +337,7 @@ Code  Seq#    Include File                                           Comments
>  0xB4  00-0F  linux/gpio.h                                            <mailto:linux-gpio@vger.kernel.org>
>  0xB5  00-0F  uapi/linux/rpmsg.h                                      <mailto:linux-remoteproc@vger.kernel.org>
>  0xB6  all    linux/fpga-dfl.h
> +0xB7  all    uapi/linux/remoteproc_cdev.h			     <mailto:linux-remoteproc@vger.kernel.org>
>  0xC0  00-0F  linux/usb/iowarrior.h
>  0xCA  00-0F  uapi/misc/cxl.h
>  0xCA  10-2F  uapi/misc/ocxl.h
> diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
> index de3862c..6374b79 100644
> --- a/drivers/remoteproc/Kconfig
> +++ b/drivers/remoteproc/Kconfig
> @@ -14,6 +14,15 @@ config REMOTEPROC
>  
>  if REMOTEPROC
>  
> +config REMOTEPROC_CDEV
> +	bool "Remoteproc character device interface"
> +	help
> +	  Say y here to have a character device interface for Remoteproc

s/Remoteproc/"the remoteproc"

> +	  framework. Userspace can boot/shutdown remote processors through
> +	  this interface.
> +
> +	  It's safe to say N if you don't want to use this interface.
> +
>  config IMX_REMOTEPROC
>  	tristate "IMX6/7 remoteproc support"
>  	depends on ARCH_MXC
> diff --git a/drivers/remoteproc/Makefile b/drivers/remoteproc/Makefile
> index e30a1b1..b7d4f77 100644
> --- a/drivers/remoteproc/Makefile
> +++ b/drivers/remoteproc/Makefile
> @@ -9,6 +9,7 @@ remoteproc-y				+= remoteproc_debugfs.o
>  remoteproc-y				+= remoteproc_sysfs.o
>  remoteproc-y				+= remoteproc_virtio.o
>  remoteproc-y				+= remoteproc_elf_loader.o
> +obj-$(CONFIG_REMOTEPROC_CDEV)		+= remoteproc_cdev.o
>  obj-$(CONFIG_IMX_REMOTEPROC)		+= imx_rproc.o
>  obj-$(CONFIG_MTK_SCP)			+= mtk_scp.o mtk_scp_ipi.o
>  obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o
> diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
> new file mode 100644
> index 0000000..65142ec
> --- /dev/null
> +++ b/drivers/remoteproc/remoteproc_cdev.c
> @@ -0,0 +1,143 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Character device interface driver for Remoteproc framework.
> + *
> + * Copyright (c) 2020, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/cdev.h>
> +#include <linux/fs.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/remoteproc.h>
> +#include <uapi/linux/remoteproc_cdev.h>
> +#include <linux/uaccess.h>
> +
> +#include "remoteproc_internal.h"
> +
> +#define NUM_RPROC_DEVICES	64
> +static dev_t rproc_major;
> +
> +static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf,
> +				 size_t len, loff_t *pos)
> +{
> +	struct rproc *rproc = container_of(filp->f_inode->i_cdev,
> +					   struct rproc, char_dev);
> +	int ret = 0;
> +	char cmd[10];
> +
> +	if (!len || len > sizeof(cmd))
> +		return -EINVAL;
> +
> +	ret = copy_from_user(cmd, buf, sizeof(cmd));
> +	if (ret)
> +		return -EFAULT;
> +
> +	if (sysfs_streq(cmd, "start")) {
> +		if (rproc->state == RPROC_RUNNING)
> +			return -EBUSY;
> +
> +		ret = rproc_boot(rproc);
> +		if (ret)
> +			dev_err(&rproc->dev, "Boot failed:%d\n", ret);
> +	} else if (sysfs_streq(cmd, "stop")) {
> +		if (rproc->state == RPROC_OFFLINE)
> +			return -ENXIO;
> +
> +		rproc_shutdown(rproc);
> +	} else {
> +		dev_err(&rproc->dev, "Unrecognized option\n");
> +		ret = -EINVAL;
> +	}
> +
> +	return ret ? ret : len;
> +}
> +
> +static long rproc_device_ioctl(struct file *filp, unsigned int ioctl,
> +				unsigned long arg)
> +{
> +	struct rproc *rproc = container_of(filp->f_inode->i_cdev,
> +					   struct rproc, char_dev);
> +	void __user *argp = (void __user *)arg;
> +	int ret;
> +	bool param;
> +
> +	switch (ioctl) {
> +	case RPROC_SET_SHUTDOWN_ON_RELEASE:
> +		ret = copy_from_user(&param, argp, sizeof(bool));
> +		if (ret) {
> +			dev_err(&rproc->dev, "Data copy from userspace failed\n");
> +			return -EINVAL;
> +		}
> +		rproc->cdev_put_on_release = param;
> +		break;
> +	case RPROC_GET_SHUTDOWN_ON_RELEASE:
> +		ret = copy_to_user(argp, &rproc->cdev_put_on_release,
> +				   sizeof(bool));
> +		if (ret) {
> +			dev_err(&rproc->dev, "Data copy to userspace failed\n");
> +			return -EINVAL;
> +		}
> +		break;
> +	default:
> +		dev_err(&rproc->dev, "Unsupported ioctl\n");
> +		return -EINVAL;
> +	}
> +	return 0;
> +}
> +
> +static int rproc_cdev_release(struct inode *inode, struct file *filp)
> +{
> +	struct rproc *rproc = container_of(inode->i_cdev, struct rproc,
> +					   char_dev);
> +
> +	if (rproc->cdev_put_on_release && rproc->state != RPROC_OFFLINE)
> +		rproc_shutdown(rproc);
> +
> +	return 0;
> +}
> +
> +
> +static const struct file_operations rproc_fops = {
> +	.write = rproc_cdev_write,
> +	.unlocked_ioctl = rproc_device_ioctl,

Because this is available on any kind of system it is probably best to provide
an compat_ioctl.

> +	.release = rproc_cdev_release,
> +};
> +
> +int rproc_char_device_add(struct rproc *rproc)
> +{
> +	int ret;
> +	dev_t cdevt;
> +
> +	cdev_init(&rproc->char_dev, &rproc_fops);
> +	rproc->char_dev.owner = THIS_MODULE;
> +
> +	cdevt = MKDEV(MAJOR(rproc_major), rproc->index);
> +	ret = cdev_add(&rproc->char_dev, cdevt, 1);
> +	if (ret < 0)
> +		goto out;
> +
> +	rproc->dev.devt = cdevt;
> +out:
> +	return ret;
> +}
> +
> +void rproc_char_device_remove(struct rproc *rproc)
> +{
> +	__unregister_chrdev(MAJOR(rproc->dev.devt), rproc->index, 1, "rproc");
> +}
> +
> +void __init rproc_init_cdev(void)
> +{
> +	int ret;
> +
> +	ret = alloc_chrdev_region(&rproc_major, 0, NUM_RPROC_DEVICES, "rproc");
> +	if (ret < 0)
> +		pr_err("Failed to alloc rproc_cdev region, err %d\n", ret);
> +}
> +
> +void __exit rproc_exit_cdev(void)
> +{
> +	unregister_chrdev_region(MKDEV(MAJOR(rproc_major), 0),
> +				 NUM_RPROC_DEVICES);

Why not simply using rproc_major here?

> +}
> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
> index 493ef92..fb9d891 100644
> --- a/drivers/remoteproc/remoteproc_internal.h
> +++ b/drivers/remoteproc/remoteproc_internal.h
> @@ -47,6 +47,27 @@ struct dentry *rproc_create_trace_file(const char *name, struct rproc *rproc,
>  int rproc_init_sysfs(void);
>  void rproc_exit_sysfs(void);
>  
> +#ifdef CONFIG_REMOTEPROC_CDEV
> +void rproc_init_cdev(void);
> +void rproc_exit_cdev(void);
> +int rproc_char_device_add(struct rproc *rproc);
> +void rproc_char_device_remove(struct rproc *rproc);
> +#else
> +static inline void rproc_init_cdev(void)
> +{
> +}
> +static inline void rproc_exit_cdev(void)
> +{
> +}
> +static inline int rproc_char_device_add(struct rproc *rproc)
> +{
> +	return 0;

Add a comment that mentions the support of the character interface is optional
and as such and error is not generated if not available on the system.

> +}
> +static inline void  rproc_char_device_remove(struct rproc *rproc)
> +{
> +}
> +#endif
> +
>  void rproc_free_vring(struct rproc_vring *rvring);
>  int rproc_alloc_vring(struct rproc_vdev *rvdev, int i);
>  
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 16ad666..9bd2ff5 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -40,6 +40,7 @@
>  #include <linux/virtio.h>
>  #include <linux/completion.h>
>  #include <linux/idr.h>
> +#include <linux/cdev.h>
>  #include <linux/of.h>
>  
>  /**
> @@ -514,6 +515,8 @@ struct rproc {
>  	bool auto_boot;
>  	struct list_head dump_segments;
>  	int nb_vdev;
> +	struct cdev char_dev;
> +	bool cdev_put_on_release;

Please add documentation for these.  Also note you will have to rebase your work
on the latest rproc-next.

Thanks,
Mathieu

>  };
>  
>  /**
> diff --git a/include/uapi/linux/remoteproc_cdev.h b/include/uapi/linux/remoteproc_cdev.h
> new file mode 100644
> index 0000000..3975120
> --- /dev/null
> +++ b/include/uapi/linux/remoteproc_cdev.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> +/*
> + * IOCTLs for Remoteproc's character device interface.
> + *
> + * Copyright (c) 2020, The Linux Foundation. All rights reserved.
> + */
> +
> +
> +#ifndef _UAPI_REMOTEPROC_CDEV_H_
> +#define _UAPI_REMOTEPROC_CDEV_H_
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +
> +#define RPROC_MAGIC	0xB7
> +
> +#define RPROC_SET_SHUTDOWN_ON_RELEASE _IOW(RPROC_MAGIC, 1, int)
> +#define RPROC_GET_SHUTDOWN_ON_RELEASE _IOR(RPROC_MAGIC, 2, int)
> +
> +#endif
> -- 
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