// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/uio/uio.c
 *
 * Copyright(C) 2005, Benedikt Spranger <b.spranger@linutronix.de>
 * Copyright(C) 2005, Linutronix GmbH, Thomas Gleixner <tglx@kernel.org>
 * Copyright(C) 2006, Hans J. Koch <hjk@hansjkoch.de>
 * Copyright(C) 2006, Greg Kroah-Hartman <greg@kroah.com>
 *
 * Userspace IO
 *
 * Base Functions
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/idr.h>
#include <linux/sched/signal.h>
#include <linux/string.h>
#include <linux/kobject.h>
#include <linux/cdev.h>
#include <linux/uio_driver.h>
#include <linux/dma-mapping.h>

#define UIO_MAX_DEVICES         (1U << MINORBITS)

static int uio_major;
static struct cdev *uio_cdev;
static DEFINE_IDR(uio_idr);
static const struct file_operations uio_fops;

/* Protect idr accesses */
static DEFINE_MUTEX(minor_lock);

/*
 * attributes
 */

struct uio_map {
        struct kobject kobj;
        struct uio_mem *mem;
};
#define to_map(map) container_of(map, struct uio_map, kobj)

static ssize_t map_name_show(struct uio_mem *mem, char *buf)
{
        if (unlikely(!mem->name))
                mem->name = "";

        return sprintf(buf, "%s\n", mem->name);
}

static ssize_t map_addr_show(struct uio_mem *mem, char *buf)
{
        return sprintf(buf, "%pa\n", &mem->addr);
}

static ssize_t map_size_show(struct uio_mem *mem, char *buf)
{
        return sprintf(buf, "%pa\n", &mem->size);
}

static ssize_t map_offset_show(struct uio_mem *mem, char *buf)
{
        return sprintf(buf, "0x%llx\n", (unsigned long long)mem->offs);
}

struct map_sysfs_entry {
        struct attribute attr;
        ssize_t (*show)(struct uio_mem *, char *);
        ssize_t (*store)(struct uio_mem *, const char *, size_t);
};

static struct map_sysfs_entry name_attribute =
        __ATTR(name, S_IRUGO, map_name_show, NULL);
static struct map_sysfs_entry addr_attribute =
        __ATTR(addr, S_IRUGO, map_addr_show, NULL);
static struct map_sysfs_entry size_attribute =
        __ATTR(size, S_IRUGO, map_size_show, NULL);
static struct map_sysfs_entry offset_attribute =
        __ATTR(offset, S_IRUGO, map_offset_show, NULL);

static struct attribute *map_attrs[] = {
        &name_attribute.attr,
        &addr_attribute.attr,
        &size_attribute.attr,
        &offset_attribute.attr,
        NULL,   /* need to NULL terminate the list of attributes */
};
ATTRIBUTE_GROUPS(map);

static void map_release(struct kobject *kobj)
{
        struct uio_map *map = to_map(kobj);
        kfree(map);
}

static ssize_t map_type_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct uio_map *map = to_map(kobj);
        struct uio_mem *mem = map->mem;
        struct map_sysfs_entry *entry;

        entry = container_of(attr, struct map_sysfs_entry, attr);

        if (!entry->show)
                return -EIO;

        return entry->show(mem, buf);
}

static const struct sysfs_ops map_sysfs_ops = {
        .show = map_type_show,
};

static const struct kobj_type map_attr_type = {
        .release        = map_release,
        .sysfs_ops      = &map_sysfs_ops,
        .default_groups = map_groups,
};

struct uio_portio {
        struct kobject kobj;
        struct uio_port *port;
};
#define to_portio(portio) container_of(portio, struct uio_portio, kobj)

static ssize_t portio_name_show(struct uio_port *port, char *buf)
{
        if (unlikely(!port->name))
                port->name = "";

        return sprintf(buf, "%s\n", port->name);
}

static ssize_t portio_start_show(struct uio_port *port, char *buf)
{
        return sprintf(buf, "0x%lx\n", port->start);
}

static ssize_t portio_size_show(struct uio_port *port, char *buf)
{
        return sprintf(buf, "0x%lx\n", port->size);
}

static ssize_t portio_porttype_show(struct uio_port *port, char *buf)
{
        const char *porttypes[] = {"none", "x86", "gpio", "other"};

        if ((port->porttype < 0) || (port->porttype > UIO_PORT_OTHER))
                return -EINVAL;

        return sprintf(buf, "port_%s\n", porttypes[port->porttype]);
}

struct portio_sysfs_entry {
        struct attribute attr;
        ssize_t (*show)(struct uio_port *, char *);
        ssize_t (*store)(struct uio_port *, const char *, size_t);
};

static struct portio_sysfs_entry portio_name_attribute =
        __ATTR(name, S_IRUGO, portio_name_show, NULL);
static struct portio_sysfs_entry portio_start_attribute =
        __ATTR(start, S_IRUGO, portio_start_show, NULL);
static struct portio_sysfs_entry portio_size_attribute =
        __ATTR(size, S_IRUGO, portio_size_show, NULL);
static struct portio_sysfs_entry portio_porttype_attribute =
        __ATTR(porttype, S_IRUGO, portio_porttype_show, NULL);

static struct attribute *portio_attrs[] = {
        &portio_name_attribute.attr,
        &portio_start_attribute.attr,
        &portio_size_attribute.attr,
        &portio_porttype_attribute.attr,
        NULL,
};
ATTRIBUTE_GROUPS(portio);

static void portio_release(struct kobject *kobj)
{
        struct uio_portio *portio = to_portio(kobj);
        kfree(portio);
}

static ssize_t portio_type_show(struct kobject *kobj, struct attribute *attr,
                             char *buf)
{
        struct uio_portio *portio = to_portio(kobj);
        struct uio_port *port = portio->port;
        struct portio_sysfs_entry *entry;

        entry = container_of(attr, struct portio_sysfs_entry, attr);

        if (!entry->show)
                return -EIO;

        return entry->show(port, buf);
}

static const struct sysfs_ops portio_sysfs_ops = {
        .show = portio_type_show,
};

static const struct kobj_type portio_attr_type = {
        .release        = portio_release,
        .sysfs_ops      = &portio_sysfs_ops,
        .default_groups = portio_groups,
};

static ssize_t name_show(struct device *dev,
                         struct device_attribute *attr, char *buf)
{
        struct uio_device *idev = dev_get_drvdata(dev);
        int ret;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                ret = -EINVAL;
                dev_err(dev, "the device has been unregistered\n");
                goto out;
        }

        ret = sprintf(buf, "%s\n", idev->info->name);

out:
        mutex_unlock(&idev->info_lock);
        return ret;
}
static DEVICE_ATTR_RO(name);

static ssize_t version_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        struct uio_device *idev = dev_get_drvdata(dev);
        int ret;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                ret = -EINVAL;
                dev_err(dev, "the device has been unregistered\n");
                goto out;
        }

        ret = sprintf(buf, "%s\n", idev->info->version);

out:
        mutex_unlock(&idev->info_lock);
        return ret;
}
static DEVICE_ATTR_RO(version);

static ssize_t event_show(struct device *dev,
                          struct device_attribute *attr, char *buf)
{
        struct uio_device *idev = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", (unsigned int)atomic_read(&idev->event));
}
static DEVICE_ATTR_RO(event);

static struct attribute *uio_attrs[] = {
        &dev_attr_name.attr,
        &dev_attr_version.attr,
        &dev_attr_event.attr,
        NULL,
};
ATTRIBUTE_GROUPS(uio);

/* UIO class infrastructure */
static struct class uio_class = {
        .name = "uio",
        .dev_groups = uio_groups,
};

static bool uio_class_registered;

/*
 * device functions
 */
static int uio_dev_add_attributes(struct uio_device *idev)
{
        int ret;
        int mi, pi;
        int map_found = 0;
        int portio_found = 0;
        struct uio_mem *mem;
        struct uio_map *map;
        struct uio_port *port;
        struct uio_portio *portio;

        for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
                mem = &idev->info->mem[mi];
                if (mem->size == 0)
                        break;
                if (!map_found) {
                        map_found = 1;
                        idev->map_dir = kobject_create_and_add("maps",
                                                        &idev->dev.kobj);
                        if (!idev->map_dir) {
                                ret = -ENOMEM;
                                goto err_map;
                        }
                }
                map = kzalloc_obj(*map);
                if (!map) {
                        ret = -ENOMEM;
                        goto err_map;
                }
                kobject_init(&map->kobj, &map_attr_type);
                map->mem = mem;
                mem->map = map;
                ret = kobject_add(&map->kobj, idev->map_dir, "map%d", mi);
                if (ret)
                        goto err_map_kobj;
                ret = kobject_uevent(&map->kobj, KOBJ_ADD);
                if (ret)
                        goto err_map_kobj;
        }

        for (pi = 0; pi < MAX_UIO_PORT_REGIONS; pi++) {
                port = &idev->info->port[pi];
                if (port->size == 0)
                        break;
                if (!portio_found) {
                        portio_found = 1;
                        idev->portio_dir = kobject_create_and_add("portio",
                                                        &idev->dev.kobj);
                        if (!idev->portio_dir) {
                                ret = -ENOMEM;
                                goto err_portio;
                        }
                }
                portio = kzalloc_obj(*portio);
                if (!portio) {
                        ret = -ENOMEM;
                        goto err_portio;
                }
                kobject_init(&portio->kobj, &portio_attr_type);
                portio->port = port;
                port->portio = portio;
                ret = kobject_add(&portio->kobj, idev->portio_dir,
                                                        "port%d", pi);
                if (ret)
                        goto err_portio_kobj;
                ret = kobject_uevent(&portio->kobj, KOBJ_ADD);
                if (ret)
                        goto err_portio_kobj;
        }

        return 0;

err_portio:
        pi--;
err_portio_kobj:
        for (; pi >= 0; pi--) {
                port = &idev->info->port[pi];
                portio = port->portio;
                kobject_put(&portio->kobj);
        }
        kobject_put(idev->portio_dir);
err_map:
        mi--;
err_map_kobj:
        for (; mi >= 0; mi--) {
                mem = &idev->info->mem[mi];
                map = mem->map;
                kobject_put(&map->kobj);
        }
        kobject_put(idev->map_dir);
        dev_err(&idev->dev, "error creating sysfs files (%d)\n", ret);
        return ret;
}

static void uio_dev_del_attributes(struct uio_device *idev)
{
        int i;
        struct uio_mem *mem;
        struct uio_port *port;

        for (i = 0; i < MAX_UIO_MAPS; i++) {
                mem = &idev->info->mem[i];
                if (mem->size == 0)
                        break;
                kobject_put(&mem->map->kobj);
        }
        kobject_put(idev->map_dir);

        for (i = 0; i < MAX_UIO_PORT_REGIONS; i++) {
                port = &idev->info->port[i];
                if (port->size == 0)
                        break;
                kobject_put(&port->portio->kobj);
        }
        kobject_put(idev->portio_dir);
}

static int uio_get_minor(struct uio_device *idev)
{
        int retval;

        mutex_lock(&minor_lock);
        retval = idr_alloc(&uio_idr, idev, 0, UIO_MAX_DEVICES, GFP_KERNEL);
        if (retval >= 0) {
                idev->minor = retval;
                retval = 0;
        } else if (retval == -ENOSPC) {
                dev_err(&idev->dev, "too many uio devices\n");
                retval = -EINVAL;
        }
        mutex_unlock(&minor_lock);
        return retval;
}

static void uio_free_minor(unsigned long minor)
{
        mutex_lock(&minor_lock);
        idr_remove(&uio_idr, minor);
        mutex_unlock(&minor_lock);
}

/**
 * uio_event_notify - trigger an interrupt event
 * @info: UIO device capabilities
 */
void uio_event_notify(struct uio_info *info)
{
        struct uio_device *idev = info->uio_dev;

        atomic_inc(&idev->event);
        wake_up_interruptible(&idev->wait);
        kill_fasync(&idev->async_queue, SIGIO, POLL_IN);
}
EXPORT_SYMBOL_GPL(uio_event_notify);

/**
 * uio_interrupt_handler - hardware interrupt handler
 * @irq: IRQ number, can be UIO_IRQ_CYCLIC for cyclic timer
 * @dev_id: Pointer to the devices uio_device structure
 */
static irqreturn_t uio_interrupt_handler(int irq, void *dev_id)
{
        struct uio_device *idev = (struct uio_device *)dev_id;
        irqreturn_t ret;

        ret = idev->info->handler(irq, idev->info);
        if (ret == IRQ_HANDLED)
                ret = IRQ_WAKE_THREAD;

        return ret;
}

/**
 * uio_interrupt_thread - irq thread handler
 * @irq: IRQ number
 * @dev_id: Pointer to the devices uio_device structure
 */
static irqreturn_t uio_interrupt_thread(int irq, void *dev_id)
{
        struct uio_device *idev = (struct uio_device *)dev_id;

        uio_event_notify(idev->info);

        return IRQ_HANDLED;
}

struct uio_listener {
        struct uio_device *dev;
        s32 event_count;
};

static int uio_open(struct inode *inode, struct file *filep)
{
        struct uio_device *idev;
        struct uio_listener *listener;
        int ret = 0;

        mutex_lock(&minor_lock);
        idev = idr_find(&uio_idr, iminor(inode));
        if (!idev) {
                ret = -ENODEV;
                mutex_unlock(&minor_lock);
                goto out;
        }
        get_device(&idev->dev);
        mutex_unlock(&minor_lock);

        if (!try_module_get(idev->owner)) {
                ret = -ENODEV;
                goto err_module_get;
        }

        listener = kmalloc_obj(*listener);
        if (!listener) {
                ret = -ENOMEM;
                goto err_alloc_listener;
        }

        listener->dev = idev;
        listener->event_count = atomic_read(&idev->event);
        filep->private_data = listener;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                mutex_unlock(&idev->info_lock);
                ret = -EINVAL;
                goto err_infoopen;
        }

        if (idev->info->open)
                ret = idev->info->open(idev->info, inode);
        mutex_unlock(&idev->info_lock);
        if (ret)
                goto err_infoopen;

        return 0;

err_infoopen:
        kfree(listener);

err_alloc_listener:
        module_put(idev->owner);

err_module_get:
        put_device(&idev->dev);

out:
        return ret;
}

static int uio_fasync(int fd, struct file *filep, int on)
{
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;

        return fasync_helper(fd, filep, on, &idev->async_queue);
}

static int uio_release(struct inode *inode, struct file *filep)
{
        int ret = 0;
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;

        mutex_lock(&idev->info_lock);
        if (idev->info && idev->info->release)
                ret = idev->info->release(idev->info, inode);
        mutex_unlock(&idev->info_lock);

        module_put(idev->owner);
        kfree(listener);
        put_device(&idev->dev);
        return ret;
}

static __poll_t uio_poll(struct file *filep, poll_table *wait)
{
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
        __poll_t ret = 0;

        mutex_lock(&idev->info_lock);
        if (!idev->info || !idev->info->irq)
                ret = EPOLLERR;
        mutex_unlock(&idev->info_lock);

        if (ret)
                return ret;

        poll_wait(filep, &idev->wait, wait);
        if (listener->event_count != atomic_read(&idev->event))
                return EPOLLIN | EPOLLRDNORM;
        return 0;
}

static ssize_t uio_read(struct file *filep, char __user *buf,
                        size_t count, loff_t *ppos)
{
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
        DECLARE_WAITQUEUE(wait, current);
        ssize_t retval = 0;
        s32 event_count;

        if (count != sizeof(s32))
                return -EINVAL;

        add_wait_queue(&idev->wait, &wait);

        do {
                mutex_lock(&idev->info_lock);
                if (!idev->info || !idev->info->irq) {
                        retval = -EIO;
                        mutex_unlock(&idev->info_lock);
                        break;
                }
                mutex_unlock(&idev->info_lock);

                set_current_state(TASK_INTERRUPTIBLE);

                event_count = atomic_read(&idev->event);
                if (event_count != listener->event_count) {
                        __set_current_state(TASK_RUNNING);
                        if (copy_to_user(buf, &event_count, count))
                                retval = -EFAULT;
                        else {
                                listener->event_count = event_count;
                                retval = count;
                        }
                        break;
                }

                if (filep->f_flags & O_NONBLOCK) {
                        retval = -EAGAIN;
                        break;
                }

                if (signal_pending(current)) {
                        retval = -ERESTARTSYS;
                        break;
                }
                schedule();
        } while (1);

        __set_current_state(TASK_RUNNING);
        remove_wait_queue(&idev->wait, &wait);

        return retval;
}

static ssize_t uio_write(struct file *filep, const char __user *buf,
                        size_t count, loff_t *ppos)
{
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
        ssize_t retval;
        s32 irq_on;

        if (count != sizeof(s32))
                return -EINVAL;

        if (copy_from_user(&irq_on, buf, count))
                return -EFAULT;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                retval = -EINVAL;
                goto out;
        }

        if (!idev->info->irq) {
                retval = -EIO;
                goto out;
        }

        if (!idev->info->irqcontrol) {
                retval = -ENOSYS;
                goto out;
        }

        retval = idev->info->irqcontrol(idev->info, irq_on);

out:
        mutex_unlock(&idev->info_lock);
        return retval ? retval : sizeof(s32);
}

static int uio_find_mem_index(struct vm_area_struct *vma)
{
        struct uio_device *idev = vma->vm_private_data;

        if (vma->vm_pgoff < MAX_UIO_MAPS) {
                if (idev->info->mem[vma->vm_pgoff].size == 0)
                        return -1;
                return (int)vma->vm_pgoff;
        }
        return -1;
}

static vm_fault_t uio_vma_fault(struct vm_fault *vmf)
{
        struct uio_device *idev = vmf->vma->vm_private_data;
        struct page *page;
        unsigned long offset;
        void *addr;
        vm_fault_t ret = 0;
        int mi;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                ret = VM_FAULT_SIGBUS;
                goto out;
        }

        mi = uio_find_mem_index(vmf->vma);
        if (mi < 0) {
                ret = VM_FAULT_SIGBUS;
                goto out;
        }

        /*
         * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
         * to use mem[N].
         */
        offset = (vmf->pgoff - mi) << PAGE_SHIFT;

        addr = (void *)(unsigned long)idev->info->mem[mi].addr + offset;
        if (idev->info->mem[mi].memtype == UIO_MEM_LOGICAL)
                page = virt_to_page(addr);
        else
                page = vmalloc_to_page(addr);
        get_page(page);
        vmf->page = page;

out:
        mutex_unlock(&idev->info_lock);

        return ret;
}

static const struct vm_operations_struct uio_logical_vm_ops = {
        .fault = uio_vma_fault,
};

static int uio_mmap_logical(struct vm_area_struct *vma)
{
        vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP);
        vma->vm_ops = &uio_logical_vm_ops;
        return 0;
}

static const struct vm_operations_struct uio_physical_vm_ops = {
#ifdef CONFIG_HAVE_IOREMAP_PROT
        .access = generic_access_phys,
#endif
};

static int uio_mmap_physical(struct vm_area_struct *vma)
{
        struct uio_device *idev = vma->vm_private_data;
        int mi = uio_find_mem_index(vma);
        struct uio_mem *mem;

        if (mi < 0)
                return -EINVAL;
        mem = idev->info->mem + mi;

        if (mem->addr & ~PAGE_MASK)
                return -ENODEV;
        if (vma->vm_end - vma->vm_start > mem->size)
                return -EINVAL;

        vma->vm_ops = &uio_physical_vm_ops;
        if (idev->info->mem[mi].memtype == UIO_MEM_PHYS)
                vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        /*
         * We cannot use the vm_iomap_memory() helper here,
         * because vma->vm_pgoff is the map index we looked
         * up above in uio_find_mem_index(), rather than an
         * actual page offset into the mmap.
         *
         * So we just do the physical mmap without a page
         * offset.
         */
        return remap_pfn_range(vma,
                               vma->vm_start,
                               mem->addr >> PAGE_SHIFT,
                               vma->vm_end - vma->vm_start,
                               vma->vm_page_prot);
}

static int uio_mmap_dma_coherent(struct vm_area_struct *vma)
{
        struct uio_device *idev = vma->vm_private_data;
        struct uio_mem *mem;
        void *addr;
        int ret = 0;
        int mi;

        mi = uio_find_mem_index(vma);
        if (mi < 0)
                return -EINVAL;

        mem = idev->info->mem + mi;

        if (mem->addr & ~PAGE_MASK)
                return -ENODEV;
        if (mem->dma_addr & ~PAGE_MASK)
                return -ENODEV;
        if (!mem->dma_device)
                return -ENODEV;
        if (vma->vm_end - vma->vm_start > mem->size)
                return -EINVAL;

        dev_warn(mem->dma_device,
                 "use of UIO_MEM_DMA_COHERENT is highly discouraged");

        /*
         * UIO uses offset to index into the maps for a device.
         * We need to clear vm_pgoff for dma_mmap_coherent.
         */
        vma->vm_pgoff = 0;

        addr = (void *)(uintptr_t)mem->addr;
        ret = dma_mmap_coherent(mem->dma_device,
                                vma,
                                addr,
                                mem->dma_addr,
                                vma->vm_end - vma->vm_start);
        vma->vm_pgoff = mi;

        return ret;
}

static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
{
        struct uio_listener *listener = filep->private_data;
        struct uio_device *idev = listener->dev;
        int mi;
        unsigned long requested_pages, actual_pages;
        int ret = 0;

        if (vma->vm_end < vma->vm_start)
                return -EINVAL;

        vma->vm_private_data = idev;

        mutex_lock(&idev->info_lock);
        if (!idev->info) {
                ret = -EINVAL;
                goto out;
        }

        mi = uio_find_mem_index(vma);
        if (mi < 0) {
                ret = -EINVAL;
                goto out;
        }

        requested_pages = vma_pages(vma);
        actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK)
                        + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
        if (requested_pages > actual_pages) {
                ret = -EINVAL;
                goto out;
        }

        if (idev->info->mmap) {
                ret = idev->info->mmap(idev->info, vma);
                goto out;
        }

        switch (idev->info->mem[mi].memtype) {
        case UIO_MEM_IOVA:
        case UIO_MEM_PHYS:
                ret = uio_mmap_physical(vma);
                break;
        case UIO_MEM_LOGICAL:
        case UIO_MEM_VIRTUAL:
                ret = uio_mmap_logical(vma);
                break;
        case UIO_MEM_DMA_COHERENT:
                ret = uio_mmap_dma_coherent(vma);
                break;
        default:
                ret = -EINVAL;
        }

 out:
        mutex_unlock(&idev->info_lock);
        return ret;
}

static const struct file_operations uio_fops = {
        .owner          = THIS_MODULE,
        .open           = uio_open,
        .release        = uio_release,
        .read           = uio_read,
        .write          = uio_write,
        .mmap           = uio_mmap,
        .poll           = uio_poll,
        .fasync         = uio_fasync,
        .llseek         = noop_llseek,
};

static int uio_major_init(void)
{
        static const char name[] = "uio";
        struct cdev *cdev = NULL;
        dev_t uio_dev = 0;
        int result;

        result = alloc_chrdev_region(&uio_dev, 0, UIO_MAX_DEVICES, name);
        if (result)
                goto out;

        result = -ENOMEM;
        cdev = cdev_alloc();
        if (!cdev)
                goto out_unregister;

        cdev->owner = THIS_MODULE;
        cdev->ops = &uio_fops;
        kobject_set_name(&cdev->kobj, "%s", name);

        result = cdev_add(cdev, uio_dev, UIO_MAX_DEVICES);
        if (result)
                goto out_put;

        uio_major = MAJOR(uio_dev);
        uio_cdev = cdev;
        return 0;
out_put:
        kobject_put(&cdev->kobj);
out_unregister:
        unregister_chrdev_region(uio_dev, UIO_MAX_DEVICES);
out:
        return result;
}

static void uio_major_cleanup(void)
{
        unregister_chrdev_region(MKDEV(uio_major, 0), UIO_MAX_DEVICES);
        cdev_del(uio_cdev);
}

static int init_uio_class(void)
{
        int ret;

        /* This is the first time in here, set everything up properly */
        ret = uio_major_init();
        if (ret)
                goto exit;

        ret = class_register(&uio_class);
        if (ret) {
                printk(KERN_ERR "class_register failed for uio\n");
                goto err_class_register;
        }

        uio_class_registered = true;

        return 0;

err_class_register:
        uio_major_cleanup();
exit:
        return ret;
}

static void release_uio_class(void)
{
        uio_class_registered = false;
        class_unregister(&uio_class);
        uio_major_cleanup();
}

static void uio_device_release(struct device *dev)
{
        struct uio_device *idev = dev_get_drvdata(dev);

        kfree(idev);
}

/**
 * __uio_register_device - register a new userspace IO device
 * @owner:      module that creates the new device
 * @parent:     parent device
 * @info:       UIO device capabilities
 *
 * returns zero on success or a negative error code.
 */
int __uio_register_device(struct module *owner,
                          struct device *parent,
                          struct uio_info *info)
{
        struct uio_device *idev;
        int ret = 0;

        if (!uio_class_registered)
                return -EPROBE_DEFER;

        if (!parent || !info || !info->name || !info->version)
                return -EINVAL;

        info->uio_dev = NULL;

        idev = kzalloc_obj(*idev);
        if (!idev) {
                return -ENOMEM;
        }

        idev->owner = owner;
        idev->info = info;
        mutex_init(&idev->info_lock);
        init_waitqueue_head(&idev->wait);
        atomic_set(&idev->event, 0);

        ret = uio_get_minor(idev);
        if (ret) {
                kfree(idev);
                return ret;
        }

        device_initialize(&idev->dev);
        idev->dev.devt = MKDEV(uio_major, idev->minor);
        idev->dev.class = &uio_class;
        idev->dev.parent = parent;
        idev->dev.release = uio_device_release;
        dev_set_drvdata(&idev->dev, idev);

        ret = dev_set_name(&idev->dev, "uio%d", idev->minor);
        if (ret)
                goto err_device_create;

        ret = device_add(&idev->dev);
        if (ret)
                goto err_device_create;

        ret = uio_dev_add_attributes(idev);
        if (ret)
                goto err_uio_dev_add_attributes;

        info->uio_dev = idev;

        if (info->irq && (info->irq != UIO_IRQ_CUSTOM)) {
                /*
                 * Note that we deliberately don't use devm_request_irq
                 * here. The parent module can unregister the UIO device
                 * and call pci_disable_msi, which requires that this
                 * irq has been freed. However, the device may have open
                 * FDs at the time of unregister and therefore may not be
                 * freed until they are released.
                 */
                ret = request_threaded_irq(info->irq, uio_interrupt_handler, uio_interrupt_thread,
                                           info->irq_flags, info->name, idev);
                if (ret) {
                        info->uio_dev = NULL;
                        goto err_request_irq;
                }
        }

        return 0;

err_request_irq:
        uio_dev_del_attributes(idev);
err_uio_dev_add_attributes:
        device_del(&idev->dev);
err_device_create:
        uio_free_minor(idev->minor);
        put_device(&idev->dev);
        return ret;
}
EXPORT_SYMBOL_GPL(__uio_register_device);

static void devm_uio_unregister_device(struct device *dev, void *res)
{
        uio_unregister_device(*(struct uio_info **)res);
}

/**
 * __devm_uio_register_device - Resource managed uio_register_device()
 * @owner:      module that creates the new device
 * @parent:     parent device
 * @info:       UIO device capabilities
 *
 * returns zero on success or a negative error code.
 */
int __devm_uio_register_device(struct module *owner,
                               struct device *parent,
                               struct uio_info *info)
{
        struct uio_info **ptr;
        int ret;

        ptr = devres_alloc(devm_uio_unregister_device, sizeof(*ptr),
                           GFP_KERNEL);
        if (!ptr)
                return -ENOMEM;

        *ptr = info;
        ret = __uio_register_device(owner, parent, info);
        if (ret) {
                devres_free(ptr);
                return ret;
        }

        devres_add(parent, ptr);

        return 0;
}
EXPORT_SYMBOL_GPL(__devm_uio_register_device);

/**
 * uio_unregister_device - unregister a industrial IO device
 * @info:       UIO device capabilities
 *
 */
void uio_unregister_device(struct uio_info *info)
{
        struct uio_device *idev;
        unsigned long minor;

        if (!info || !info->uio_dev)
                return;

        idev = info->uio_dev;
        minor = idev->minor;

        mutex_lock(&idev->info_lock);
        uio_dev_del_attributes(idev);

        if (info->irq && info->irq != UIO_IRQ_CUSTOM)
                free_irq(info->irq, idev);

        idev->info = NULL;
        mutex_unlock(&idev->info_lock);

        wake_up_interruptible(&idev->wait);
        kill_fasync(&idev->async_queue, SIGIO, POLL_HUP);

        uio_free_minor(minor);
        device_unregister(&idev->dev);

        return;
}
EXPORT_SYMBOL_GPL(uio_unregister_device);

static int __init uio_init(void)
{
        return init_uio_class();
}

static void __exit uio_exit(void)
{
        release_uio_class();
        idr_destroy(&uio_idr);
}

module_init(uio_init)
module_exit(uio_exit)
MODULE_DESCRIPTION("Userspace IO core module");
MODULE_LICENSE("GPL v2");