Date:   Wed, 1 Jul 2020 14:13:53 +0200
From:   Arnaud POULIQUEN <arnaud.pouliquen@...com>
To:     Siddharth Gupta <sidgup@...eaurora.org>,
        "rishabhb@...eaurora.org" <rishabhb@...eaurora.org>
CC:     "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>,
        "ohad@...ery.com" <ohad@...ery.com>,
        "tsoni@...eaurora.org" <tsoni@...eaurora.org>,
        "psodagud@...eaurora.org" <psodagud@...eaurora.org>,
        "linux-remoteproc-owner@...r.kernel.org" 
        <linux-remoteproc-owner@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] remoteproc: Add remoteproc character device
 interface



On 7/1/20 12:02 AM, Siddharth Gupta wrote:
> 
> On 6/30/2020 12:43 AM, Arnaud POULIQUEN wrote:
>>
>> On 6/30/20 7:38 AM, Siddharth Gupta wrote:
>>> On 6/17/2020 1:44 AM, Arnaud POULIQUEN wrote:
>>>> On 6/16/20 9:56 PM, rishabhb@...eaurora.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@...eaurora.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@...r.kernel.org>
>>>>>>>    0xB5  00-0F  uapi/linux/rpmsg.h
>>>>>>> <mailto:linux-remoteproc@...r.kernel.org>
>>>>>>>    0xB6  all    linux/fpga-dfl.h
>>>>>>> +0xB7  all    uapi/linux/remoteproc_cdev.h			
>>>>>>> <mailto:linux-remoteproc@...r.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?
>> Regarding remoteproc_sysfs.c[1], seems that the -EINVAL return would be coherent.
> Okay sure.
>> It would probably also be better to replace your condition with
>> 	if (rproc->state != RPROC_RUNNING)
> Will do.
>>   
>>
>> [1] https://elixir.bootlin.com/linux/latest/source/drivers/remoteproc/remoteproc_sysfs.c#L104
>>
>> Regards,
>> Arnaud
>>
>>> 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
> 
> I don't see any for of comments that describe in detail the IOCTL usage, 
> i.e.,
> input parameters, etc. Could you provide an example so I can follow it?
> 
> If not, should I instead put them in Documentation/remoteproc.txt?

Bjorn and Mathieu are the right persons to decide on the best place.

Here are 2 exemples of "inline" documented IOCTRLs.

https://elixir.bootlin.com/linux/latest/source/arch/s390/include/uapi/asm/tape390.h#L15
https://elixir.bootlin.com/linux/latest/source/drivers/net/wan/cosa.h#L63 

Could be something like that:

/*
 * The RPROC_SET_SHUTDOWN_ON_RELEASE ioctl allows to enable/disable the 
 * automatic remote processors shutdown when the controlling userpsace
 * closes the char device interface.
 *
 * input parameter: integer
 *   0    : disable automatic shutdown
 *   other: enable automatic shutdown
 */ 
#define RPROC_SET_SHUTDOWN_ON_RELEASE _IOW(RPROC_MAGIC, 1, int)

/*
 * The RPROC_GET_SHUTDOWN_ON_RELEASE ioctl gets information about the 
 * automatic remote processors shutdown when the controlling userpsace
 * closes the char device interface.
 *
 * output parameter: integer
 *   0: automatic shutdown disable
 *   1: automatic shutdown enable
 */ 
#define RPROC_GET_SHUTDOWN_ON_RELEASE _IOR(RPROC_MAGIC, 2, int)


Regards,
Arnaud
> 
> Thanks,
> Sid
> 
>>>>
>>>>>> Thanks,
>>>>>> Arnaud

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