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Date:   Tue, 16 Jun 2020 12:56:40 -0700
From:   rishabhb@codeaurora.org
To:     Arnaud POULIQUEN <arnaud.pouliquen@st.com>
Cc:     linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org,
        bjorn.andersson@linaro.org, mathieu.poirier@linaro.org,
        ohad@wizery.com, tsoni@codeaurora.org, psodagud@codeaurora.org,
        sidgup@codeaurora.org, linux-remoteproc-owner@vger.kernel.org
Subject: Re: [PATCH v3 1/2] remoteproc: Add remoteproc character device
 interface
In-Reply-To: <d72ead5a-b25a-d4e2-4bbf-1790d2a64fb8@st.com>
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>
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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) ?
> 
>> +
>> +		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?
> 
> Thanks,
> Arnaud