[PATCH v4 1/2] remoteproc: Add remoteproc character device interface

From: Siddharth Gupta
Date: Tue Jul 07 2020 - 15:08:28 EST

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.

Signed-off-by: Rishabh Bhatnagar <rishabhb@xxxxxxxxxxxxxx>
Signed-off-by: Siddharth Gupta <sidgup@xxxxxxxxxxxxxx>
---
Documentation/userspace-api/ioctl/ioctl-number.rst | 1 +
drivers/remoteproc/Kconfig | 9 ++
drivers/remoteproc/Makefile | 1 +
drivers/remoteproc/remoteproc_cdev.c | 146 +++++++++++++++++++++
drivers/remoteproc/remoteproc_internal.h | 28 ++++
include/linux/remoteproc.h | 5 +
include/uapi/linux/remoteproc_cdev.h | 37 ++++++
7 files changed, 227 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 59472cd..2a19883 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -339,6 +339,7 @@ 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 c4d1731..652060f 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 the 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 e8b886e..311ae3f 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-$(CONFIG_INGENIC_VPU_RPROC) += ingenic_rproc.o
obj-$(CONFIG_MTK_SCP) += mtk_scp.o mtk_scp_ipi.o
diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
new file mode 100644
index 0000000..8a0eb47
--- /dev/null
+++ b/drivers/remoteproc/remoteproc_cdev.c
@@ -0,0 +1,146 @@
+// 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/compat.h>
+#include <linux/remoteproc.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/remoteproc_cdev.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_RUNNING)
+ return -EINVAL;
+
+ 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 = compat_ptr(arg);
+ int ret;
+ int32_t param;
+
+ switch (ioctl) {
+ case RPROC_SET_SHUTDOWN_ON_RELEASE:
+ ret = copy_from_user(&param, argp, sizeof(int32_t));
+ if (ret) {
+ dev_err(&rproc->dev, "Data copy from userspace failed\n");
+ return -EFAULT;
+ }
+ mutex_lock(&rproc->lock);
+ rproc->cdev_put_on_release = param ? true : false;
+ mutex_unlock(&rproc->lock);
+ break;
+ case RPROC_GET_SHUTDOWN_ON_RELEASE:
+ mutex_lock(&rproc->lock);
+ ret = copy_to_user(argp, &rproc->cdev_put_on_release, sizeof(bool));
+ mutex_unlock(&rproc->lock);
+ if (ret) {
+ dev_err(&rproc->dev, "Data copy to userspace failed\n");
+ return -EFAULT;
+ }
+ 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);
+ bool release;
+
+ mutex_lock(&rproc->lock);
+ release = rproc->cdev_put_on_release;
+ mutex_unlock(&rproc->lock);
+
+ if (release && rproc->state == RPROC_RUNNING)
+ rproc_shutdown(rproc);
+
+ return 0;
+}
+
+static const struct file_operations rproc_fops = {
+ .write = rproc_cdev_write,
+ .compat_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(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(rproc_major, rproc->index, 1, "remoteproc");
+}
+
+void __init rproc_init_cdev(void)
+{
+ int ret;
+
+ ret = alloc_chrdev_region(&rproc_major, 0, NUM_RPROC_DEVICES, "remoteproc");
+ 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(rproc_major, 0), NUM_RPROC_DEVICES);
+}
diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
index 4ba7cb5..f091ddc 100644
--- a/drivers/remoteproc/remoteproc_internal.h
+++ b/drivers/remoteproc/remoteproc_internal.h
@@ -47,6 +47,34 @@ extern struct class rproc_class;
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)
+{
+}
+
+/*
+ * The character device interface is an optional feature, if it is not enabled
+ * the function should not return an error.
+ */
+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 e7b7bab..669cbfb 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>

/**
@@ -488,6 +489,8 @@ struct rproc_dump_segment {
* @auto_boot: flag to indicate if remote processor should be auto-started
* @dump_segments: list of segments in the firmware
* @nb_vdev: number of vdev currently handled by rproc
+ * @char_dev: character device of the rproc
+ * @cdev_put_on_release: flag to indicate if remoteproc should be shutdown on @char_dev release
*/
struct rproc {
struct list_head node;
@@ -523,6 +526,8 @@ struct rproc {
int nb_vdev;
u8 elf_class;
u16 elf_machine;
+ struct cdev char_dev;
+ bool cdev_put_on_release;
};

/**
diff --git a/include/uapi/linux/remoteproc_cdev.h b/include/uapi/linux/remoteproc_cdev.h
new file mode 100644
index 0000000..c43768e
--- /dev/null
+++ b/include/uapi/linux/remoteproc_cdev.h
@@ -0,0 +1,37 @@
+/* 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
+
+/*
+ * The RPROC_SET_SHUTDOWN_ON_RELEASE ioctl allows to enable/disable the shutdown of a remote
+ * processor automatically 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, __s32)
+
+/*
+ * The RPROC_GET_SHUTDOWN_ON_RELEASE ioctl gets information about whether the automatic shutdown of
+ * a remote processor is enabled or disabled when the controlling userspace closes the char device
+ * interface.
+ *
+ * output parameter: integer
+ * 0 : automatic shutdown disable
+ * other : automatic shutdown enable
+ */
+#define RPROC_GET_SHUTDOWN_ON_RELEASE _IOR(RPROC_MAGIC, 2, __s32)
+
+#endif
--
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