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

[Siddharth Gupta <sidgup@codeaurora.org>]

On 6/17/2020 1:44 AM, Arnaud POULIQUEN wrote:
>
> On 6/16/20 9:56 PM, rishabhb@codeaurora.org wrote:
>> On 2020-04-30 01:30, Arnaud POULIQUEN wrote:
>>> Hi Rishabh,
>>>
>>>
>>> On 4/21/20 8:10 PM, 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.
>>>>
>>> Thanks for intruducing Ioctl, this will help for future evolutions.
>>>
>>>> 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
>>>> +	  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;
>>> returning ENXIO in this case seems to me no appropriate , what about
>>> EPERM or
>>> EINVAL (rproc_sysfs) ?

I think EPERM would indicate the operation is not permitted on the 
device, and
EINVAL would indicate that the command/string they wrote to the char device
is not a valid command/string. I guess even ENXIO may not be appropriate?

In that case we could use EHOSTDOWN or ESHUTDOWN, thoughts?

Thanks,
Sid

>>>
>>>> +
>>>> +		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;
>>> argp is an void value, where cdev_put_on_release is a bool a check or
>>> a conversion  seems
>>> missing
>>>
>>>> +		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,
>>>> +	.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");
>>> "remoteproc"instead of "rproc" (in line with sysfs and debugfs naming)
>>> .
>>>
>>>> +	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);
>>>> +}
>>>> 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;
>>>> +}
>>>> +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;
>>>>   };
>>> These parameters are local variables of rproc_cdev. Could be defined
>>> in a separate structure.
>>> with a pointer in rproc to this structure.
>>>
>>>>   /**
>>>> 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
>>>>
>>> IOCTLs should probaly be documented.
>> I have added documentation to
>> Documentation/userspace-api/ioctl/ioctl-number.rst
>> Is there another place where I need to add documentation for this?
> Could you add in this file comments that describe
> the IOCTL usage and associated parameter?
>
> Regards,
> Arnaud
>
>>> Thanks,
>>> Arnaud