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

From: Siddharth Gupta
Date: Tue Jun 30 2020 - 18:02:53 EST


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@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxxxx>
0xB5 00-0F uapi/linux/rpmsg.h
<mailto:linux-remoteproc@xxxxxxxxxxxxxxx>
0xB6 all linux/fpga-dfl.h
+0xB7 all uapi/linux/remoteproc_cdev.h
<mailto:linux-remoteproc@xxxxxxxxxxxxxxx>
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?

Thanks,
Sid


Thanks,
Arnaud