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Subject: Re: [PATCH v3 1/2] remoteproc: Add remoteproc character device
 interface
To:     Siddharth Gupta <sidgup@codeaurora.org>,
        "rishabhb@codeaurora.org" <rishabhb@codeaurora.org>
CC:     "linux-remoteproc@vger.kernel.org" <linux-remoteproc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
        "mathieu.poirier@linaro.org" <mathieu.poirier@linaro.org>,
        "ohad@wizery.com" <ohad@wizery.com>,
        "tsoni@codeaurora.org" <tsoni@codeaurora.org>,
        "psodagud@codeaurora.org" <psodagud@codeaurora.org>,
        "linux-remoteproc-owner@vger.kernel.org" 
        <linux-remoteproc-owner@vger.kernel.org>
References: <1587492618-15896-1-git-send-email-rishabhb@codeaurora.org>
 <1587492618-15896-2-git-send-email-rishabhb@codeaurora.org>
 <d72ead5a-b25a-d4e2-4bbf-1790d2a64fb8@st.com>
 <d9a477cbbf19ed50af49aee7c6699e09@codeaurora.org>
 <3738198d-53d4-2fe6-a92b-2db0cd0afa68@st.com>
 <83c70517-32e4-9ce0-e1b4-2ed7a8b5c506@codeaurora.org>
From:   Arnaud POULIQUEN <arnaud.pouliquen@st.com>
Message-ID: <94541ff3-ba34-3a08-f989-6e1a0a88fbf2@st.com>
Date:   Tue, 30 Jun 2020 09:43:01 +0200
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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@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?

Regarding remoteproc_sysfs.c[1], seems that the -EINVAL return would be coherent.
It would probably also be better to replace your condition with 
	if (rproc->state != RPROC_RUNNING)
 

[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
>>
>>>> Thanks,
>>>> Arnaud