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

    Thanks,
    Arnaud

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