// SPDX-License-Identifier: GPL-2.0+
/*
 * VMEbus User access driver
 *
 * Author: Martyn Welch <martyn.welch@ge.com>
 * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
 *
 * Based on work by:
 *   Tom Armistead and Ajit Prem
 *     Copyright 2004 Motorola Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/refcount.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/ioctl.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/pci.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/syscalls.h>
#include <linux/types.h>

#include <linux/io.h>
#include <linux/uaccess.h>

#include "vme.h"
#include "vme_user.h"

#define DRIVER_NAME "vme_user"

static int bus[VME_USER_BUS_MAX];
static unsigned int bus_num;

/* Currently Documentation/admin-guide/devices.rst defines the
 * following for VME:
 *
 * 221 char     VME bus
 *                0 = /dev/bus/vme/m0           First master image
 *                1 = /dev/bus/vme/m1           Second master image
 *                2 = /dev/bus/vme/m2           Third master image
 *                3 = /dev/bus/vme/m3           Fourth master image
 *                4 = /dev/bus/vme/s0           First slave image
 *                5 = /dev/bus/vme/s1           Second slave image
 *                6 = /dev/bus/vme/s2           Third slave image
 *                7 = /dev/bus/vme/s3           Fourth slave image
 *                8 = /dev/bus/vme/ctl          Control
 *
 *              It is expected that all VME bus drivers will use the
 *              same interface.  For interface documentation see
 *              http://www.vmelinux.org/.
 *
 * However the VME driver at http://www.vmelinux.org/ is rather old and doesn't
 * even support the tsi148 chipset (which has 8 master and 8 slave windows).
 * We'll run with this for now as far as possible, however it probably makes
 * sense to get rid of the old mappings and just do everything dynamically.
 *
 * So for now, we'll restrict the driver to providing 4 masters and 4 slaves as
 * defined above and try to support at least some of the interface from
 * http://www.vmelinux.org/ as an alternative the driver can be written
 * providing a saner interface later.
 *
 * The vmelinux.org driver never supported slave images, the devices reserved
 * for slaves were repurposed to support all 8 master images on the UniverseII!
 * We shall support 4 masters and 4 slaves with this driver.
 */
#define VME_MAJOR       221     /* VME Major Device Number */
#define VME_DEVS        9       /* Number of dev entries */

#define MASTER_MINOR    0
#define MASTER_MAX      3
#define SLAVE_MINOR     4
#define SLAVE_MAX       7
#define CONTROL_MINOR   8

#define PCI_BUF_SIZE  0x20000   /* Size of one slave image buffer */

/*
 * Structure to handle image related parameters.
 */
struct image_desc {
        void *kern_buf; /* Buffer address in kernel space */
        dma_addr_t pci_buf;     /* Buffer address in PCI address space */
        unsigned long long size_buf;    /* Buffer size */
        struct mutex mutex;     /* Mutex for locking image */
        struct device *device;  /* Sysfs device */
        struct vme_resource *resource;  /* VME resource */
        int mmap_count;         /* Number of current mmap's */
};

static struct image_desc image[VME_DEVS];

static struct cdev *vme_user_cdev;              /* Character device */
static struct vme_dev *vme_user_bridge;         /* Pointer to user device */

static const struct class vme_user_sysfs_class = {
        .name = DRIVER_NAME,
};

static const int type[VME_DEVS] = {     MASTER_MINOR,   MASTER_MINOR,
                                        MASTER_MINOR,   MASTER_MINOR,
                                        SLAVE_MINOR,    SLAVE_MINOR,
                                        SLAVE_MINOR,    SLAVE_MINOR,
                                        CONTROL_MINOR
                                };

struct vme_user_vma_priv {
        unsigned int minor;
        refcount_t refcnt;
};

static ssize_t resource_to_user(int minor, char __user *buf, size_t count,
                                loff_t *ppos)
{
        ssize_t copied = 0;

        if (count > image[minor].size_buf)
                count = image[minor].size_buf;

        copied = vme_master_read(image[minor].resource, image[minor].kern_buf,
                                 count, *ppos);
        if (copied < 0)
                return (int)copied;

        if (copy_to_user(buf, image[minor].kern_buf, (unsigned long)copied))
                return -EFAULT;

        return copied;
}

static ssize_t resource_from_user(unsigned int minor, const char __user *buf,
                                  size_t count, loff_t *ppos)
{
        if (count > image[minor].size_buf)
                count = image[minor].size_buf;

        if (copy_from_user(image[minor].kern_buf, buf, (unsigned long)count))
                return -EFAULT;

        return vme_master_write(image[minor].resource, image[minor].kern_buf,
                                count, *ppos);
}

static ssize_t buffer_to_user(unsigned int minor, char __user *buf,
                              size_t count, loff_t *ppos)
{
        void *image_ptr;

        /*
         * The slave window (image_size) can exceed the fixed kern_buf
         * (size_buf == PCI_BUF_SIZE), so bound the copy to kern_buf.
         * *ppos is >= 0 here (checked by the caller), so the
         * subtraction below cannot wrap.
         */
        if (*ppos >= image[minor].size_buf)
                return 0;
        if (count > image[minor].size_buf - *ppos)
                count = image[minor].size_buf - *ppos;

        image_ptr = image[minor].kern_buf + *ppos;
        if (copy_to_user(buf, image_ptr, (unsigned long)count))
                return -EFAULT;

        return count;
}

static ssize_t buffer_from_user(unsigned int minor, const char __user *buf,
                                size_t count, loff_t *ppos)
{
        void *image_ptr;

        /*
         * The slave window (image_size) can exceed the fixed kern_buf
         * (size_buf == PCI_BUF_SIZE), so bound the copy to kern_buf.
         * *ppos is >= 0 here (checked by the caller), so the
         * subtraction below cannot wrap.
         */
        if (*ppos >= image[minor].size_buf)
                return 0;
        if (count > image[minor].size_buf - *ppos)
                count = image[minor].size_buf - *ppos;

        image_ptr = image[minor].kern_buf + *ppos;
        if (copy_from_user(image_ptr, buf, (unsigned long)count))
                return -EFAULT;

        return count;
}

static ssize_t vme_user_read(struct file *file, char __user *buf, size_t count,
                             loff_t *ppos)
{
        unsigned int minor = iminor(file_inode(file));
        ssize_t retval;
        size_t image_size;

        if (minor == CONTROL_MINOR)
                return 0;

        mutex_lock(&image[minor].mutex);

        /* XXX Do we *really* want this helper - we can use vme_*_get ? */
        image_size = vme_get_size(image[minor].resource);

        /* Ensure we are starting at a valid location */
        if ((*ppos < 0) || (*ppos > (image_size - 1))) {
                mutex_unlock(&image[minor].mutex);
                return 0;
        }

        /* Ensure not reading past end of the image */
        if (*ppos + count > image_size)
                count = image_size - *ppos;

        switch (type[minor]) {
        case MASTER_MINOR:
                retval = resource_to_user(minor, buf, count, ppos);
                break;
        case SLAVE_MINOR:
                retval = buffer_to_user(minor, buf, count, ppos);
                break;
        default:
                retval = -EINVAL;
        }

        mutex_unlock(&image[minor].mutex);
        if (retval > 0)
                *ppos += retval;

        return retval;
}

static ssize_t vme_user_write(struct file *file, const char __user *buf,
                              size_t count, loff_t *ppos)
{
        unsigned int minor = iminor(file_inode(file));
        ssize_t retval;
        size_t image_size;

        if (minor == CONTROL_MINOR)
                return 0;

        mutex_lock(&image[minor].mutex);

        image_size = vme_get_size(image[minor].resource);

        /* Ensure we are starting at a valid location */
        if ((*ppos < 0) || (*ppos > (image_size - 1))) {
                mutex_unlock(&image[minor].mutex);
                return 0;
        }

        /* Ensure not reading past end of the image */
        if (*ppos + count > image_size)
                count = image_size - *ppos;

        switch (type[minor]) {
        case MASTER_MINOR:
                retval = resource_from_user(minor, buf, count, ppos);
                break;
        case SLAVE_MINOR:
                retval = buffer_from_user(minor, buf, count, ppos);
                break;
        default:
                retval = -EINVAL;
        }

        mutex_unlock(&image[minor].mutex);

        if (retval > 0)
                *ppos += retval;

        return retval;
}

static loff_t vme_user_llseek(struct file *file, loff_t off, int whence)
{
        unsigned int minor = iminor(file_inode(file));
        size_t image_size;
        loff_t res;

        switch (type[minor]) {
        case MASTER_MINOR:
        case SLAVE_MINOR:
                mutex_lock(&image[minor].mutex);
                image_size = vme_get_size(image[minor].resource);
                res = fixed_size_llseek(file, off, whence, image_size);
                mutex_unlock(&image[minor].mutex);
                return res;
        }

        return -EINVAL;
}

/*
 * The ioctls provided by the old VME access method (the one at vmelinux.org)
 * are most certainly wrong as the effectively push the registers layout
 * through to user space. Given that the VME core can handle multiple bridges,
 * with different register layouts this is most certainly not the way to go.
 *
 * We aren't using the structures defined in the Motorola driver either - these
 * are also quite low level, however we should use the definitions that have
 * already been defined.
 */
static int vme_user_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg)
{
        struct vme_master master;
        struct vme_slave slave;
        struct vme_irq_id irq_req;
        unsigned long copied;
        unsigned int minor = iminor(inode);
        int retval;
        dma_addr_t pci_addr;
        void __user *argp = (void __user *)arg;

        switch (type[minor]) {
        case CONTROL_MINOR:
                switch (cmd) {
                case VME_IRQ_GEN:
                        copied = copy_from_user(&irq_req, argp,
                                                sizeof(irq_req));
                        if (copied) {
                                pr_warn("Partial copy from userspace\n");
                                return -EFAULT;
                        }

                        return vme_irq_generate(vme_user_bridge,
                                                  irq_req.level,
                                                  irq_req.statid);
                }
                break;
        case MASTER_MINOR:
                switch (cmd) {
                case VME_GET_MASTER:
                        memset(&master, 0, sizeof(master));

                        /* XXX  We do not want to push aspace, cycle and width
                         *      to userspace as they are
                         */
                        retval = vme_master_get(image[minor].resource,
                                                &master.enable,
                                                &master.vme_addr,
                                                &master.size, &master.aspace,
                                                &master.cycle, &master.dwidth);

                        copied = copy_to_user(argp, &master,
                                              sizeof(master));
                        if (copied) {
                                pr_warn("Partial copy to userspace\n");
                                return -EFAULT;
                        }

                        return retval;

                case VME_SET_MASTER:

                        if (image[minor].mmap_count != 0) {
                                pr_warn("Can't adjust mapped window\n");
                                return -EPERM;
                        }

                        copied = copy_from_user(&master, argp, sizeof(master));
                        if (copied) {
                                pr_warn("Partial copy from userspace\n");
                                return -EFAULT;
                        }

                        /* XXX  We do not want to push aspace, cycle and width
                         *      to userspace as they are
                         */
                        return vme_master_set(image[minor].resource,
                                master.enable, master.vme_addr, master.size,
                                master.aspace, master.cycle, master.dwidth);

                        break;
                }
                break;
        case SLAVE_MINOR:
                switch (cmd) {
                case VME_GET_SLAVE:
                        memset(&slave, 0, sizeof(slave));

                        /* XXX  We do not want to push aspace, cycle and width
                         *      to userspace as they are
                         */
                        retval = vme_slave_get(image[minor].resource,
                                               &slave.enable, &slave.vme_addr,
                                               &slave.size, &pci_addr,
                                               &slave.aspace, &slave.cycle);

                        copied = copy_to_user(argp, &slave,
                                              sizeof(slave));
                        if (copied) {
                                pr_warn("Partial copy to userspace\n");
                                return -EFAULT;
                        }

                        return retval;

                case VME_SET_SLAVE:

                        copied = copy_from_user(&slave, argp, sizeof(slave));
                        if (copied) {
                                pr_warn("Partial copy from userspace\n");
                                return -EFAULT;
                        }

                        /* XXX  We do not want to push aspace, cycle and width
                         *      to userspace as they are
                         */
                        return vme_slave_set(image[minor].resource,
                                slave.enable, slave.vme_addr, slave.size,
                                image[minor].pci_buf, slave.aspace,
                                slave.cycle);

                        break;
                }
                break;
        }

        return -EINVAL;
}

static long
vme_user_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        int ret;
        struct inode *inode = file_inode(file);
        unsigned int minor = iminor(inode);

        mutex_lock(&image[minor].mutex);
        ret = vme_user_ioctl(inode, file, cmd, arg);
        mutex_unlock(&image[minor].mutex);

        return ret;
}

static void vme_user_vm_open(struct vm_area_struct *vma)
{
        struct vme_user_vma_priv *vma_priv = vma->vm_private_data;

        refcount_inc(&vma_priv->refcnt);
}

static void vme_user_vm_close(struct vm_area_struct *vma)
{
        struct vme_user_vma_priv *vma_priv = vma->vm_private_data;
        unsigned int minor = vma_priv->minor;

        if (!refcount_dec_and_test(&vma_priv->refcnt))
                return;

        mutex_lock(&image[minor].mutex);
        image[minor].mmap_count--;
        mutex_unlock(&image[minor].mutex);

        kfree(vma_priv);
}

static int vme_user_vm_mapped(unsigned long start, unsigned long end, pgoff_t pgoff,
                              const struct file *file, void **vm_private_data)
{
        const unsigned int minor = iminor(file_inode(file));
        struct vme_user_vma_priv *vma_priv;

        mutex_lock(&image[minor].mutex);

        vma_priv = kmalloc_obj(*vma_priv);
        if (!vma_priv) {
                mutex_unlock(&image[minor].mutex);
                return -ENOMEM;
        }

        vma_priv->minor = minor;
        refcount_set(&vma_priv->refcnt, 1);
        *vm_private_data = vma_priv;
        image[minor].mmap_count++;

        mutex_unlock(&image[minor].mutex);
        return 0;
}

static const struct vm_operations_struct vme_user_vm_ops = {
        .mapped = vme_user_vm_mapped,
        .open = vme_user_vm_open,
        .close = vme_user_vm_close,
};

static int vme_user_master_mmap_prepare(unsigned int minor,
                                        struct vm_area_desc *desc)
{
        int err;

        mutex_lock(&image[minor].mutex);

        err = vme_master_mmap_prepare(image[minor].resource, desc);
        if (!err)
                desc->vm_ops = &vme_user_vm_ops;

        mutex_unlock(&image[minor].mutex);
        return err;
}

static int vme_user_mmap_prepare(struct vm_area_desc *desc)
{
        const struct file *file = desc->file;
        const unsigned int minor = iminor(file_inode(file));

        if (type[minor] == MASTER_MINOR)
                return vme_user_master_mmap_prepare(minor, desc);

        return -ENODEV;
}

static const struct file_operations vme_user_fops = {
        .read = vme_user_read,
        .write = vme_user_write,
        .llseek = vme_user_llseek,
        .unlocked_ioctl = vme_user_unlocked_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .mmap_prepare = vme_user_mmap_prepare,
};

static int vme_user_match(struct vme_dev *vdev)
{
        int i;

        int cur_bus = vme_bus_num(vdev);
        int cur_slot = vme_slot_num(vdev);

        for (i = 0; i < bus_num; i++)
                if ((cur_bus == bus[i]) && (cur_slot == vdev->num))
                        return 1;

        return 0;
}

/*
 * In this simple access driver, the old behaviour is being preserved as much
 * as practical. We will therefore reserve the buffers and request the images
 * here so that we don't have to do it later.
 */
static int vme_user_probe(struct vme_dev *vdev)
{
        int i, err;
        char *name;

        /* Save pointer to the bridge device */
        if (vme_user_bridge) {
                dev_err(&vdev->dev, "Driver can only be loaded for 1 device\n");
                err = -EINVAL;
                goto err_dev;
        }
        vme_user_bridge = vdev;

        /* Initialise descriptors */
        for (i = 0; i < VME_DEVS; i++) {
                image[i].kern_buf = NULL;
                image[i].pci_buf = 0;
                mutex_init(&image[i].mutex);
                image[i].device = NULL;
                image[i].resource = NULL;
        }

        /* Assign major and minor numbers for the driver */
        err = register_chrdev_region(MKDEV(VME_MAJOR, 0), VME_DEVS, DRIVER_NAME);
        if (err) {
                dev_warn(&vdev->dev, "Error getting Major Number %d for driver.\n",
                         VME_MAJOR);
                goto err_region;
        }

        /* Register the driver as a char device */
        vme_user_cdev = cdev_alloc();
        if (!vme_user_cdev) {
                err = -ENOMEM;
                goto err_char;
        }
        vme_user_cdev->ops = &vme_user_fops;
        vme_user_cdev->owner = THIS_MODULE;
        err = cdev_add(vme_user_cdev, MKDEV(VME_MAJOR, 0), VME_DEVS);
        if (err)
                goto err_class;

        /* Request slave resources and allocate buffers (128kB wide) */
        for (i = SLAVE_MINOR; i < (SLAVE_MAX + 1); i++) {
                /* XXX Need to properly request attributes */
                /* For ca91cx42 bridge there are only two slave windows
                 * supporting A16 addressing, so we request A24 supported
                 * by all windows.
                 */
                image[i].resource = vme_slave_request(vme_user_bridge,
                                                      VME_A24, VME_SCT);
                if (!image[i].resource) {
                        dev_warn(&vdev->dev,
                                 "Unable to allocate slave resource\n");
                        err = -ENOMEM;
                        goto err_slave;
                }
                image[i].size_buf = PCI_BUF_SIZE;
                image[i].kern_buf = vme_alloc_consistent(image[i].resource,
                                                         image[i].size_buf,
                                                         &image[i].pci_buf);
                if (!image[i].kern_buf) {
                        dev_warn(&vdev->dev,
                                 "Unable to allocate memory for buffer\n");
                        image[i].pci_buf = 0;
                        vme_slave_free(image[i].resource);
                        err = -ENOMEM;
                        goto err_slave;
                }
        }

        /*
         * Request master resources allocate page sized buffers for small
         * reads and writes
         */
        for (i = MASTER_MINOR; i < (MASTER_MAX + 1); i++) {
                /* XXX Need to properly request attributes */
                image[i].resource = vme_master_request(vme_user_bridge,
                                                       VME_A32, VME_SCT,
                                                       VME_D32);
                if (!image[i].resource) {
                        dev_warn(&vdev->dev,
                                 "Unable to allocate master resource\n");
                        err = -ENOMEM;
                        goto err_master;
                }
                image[i].size_buf = PCI_BUF_SIZE;
                image[i].kern_buf = kmalloc(image[i].size_buf, GFP_KERNEL);
                if (!image[i].kern_buf) {
                        err = -ENOMEM;
                        vme_master_free(image[i].resource);
                        goto err_master;
                }
        }

        /* Create sysfs entries - on udev systems this creates the dev files */
        err = class_register(&vme_user_sysfs_class);
        if (err) {
                dev_err(&vdev->dev, "Error creating vme_user class.\n");
                goto err_master;
        }

        /* Add sysfs Entries */
        for (i = 0; i < VME_DEVS; i++) {
                int num;

                switch (type[i]) {
                case MASTER_MINOR:
                        name = "bus/vme/m%d";
                        break;
                case CONTROL_MINOR:
                        name = "bus/vme/ctl";
                        break;
                case SLAVE_MINOR:
                        name = "bus/vme/s%d";
                        break;
                default:
                        err = -EINVAL;
                        goto err_sysfs;
                }

                num = (type[i] == SLAVE_MINOR) ? i - (MASTER_MAX + 1) : i;
                image[i].device = device_create(&vme_user_sysfs_class, NULL,
                                                MKDEV(VME_MAJOR, i), NULL,
                                                name, num);
                if (IS_ERR(image[i].device)) {
                        dev_info(&vdev->dev, "Error creating sysfs device\n");
                        err = PTR_ERR(image[i].device);
                        goto err_sysfs;
                }
        }

        return 0;

err_sysfs:
        while (i > 0) {
                i--;
                device_destroy(&vme_user_sysfs_class, MKDEV(VME_MAJOR, i));
        }
        class_unregister(&vme_user_sysfs_class);

        /* Ensure counter set correctly to unalloc all master windows */
        i = MASTER_MAX + 1;
err_master:
        while (i > MASTER_MINOR) {
                i--;
                kfree(image[i].kern_buf);
                vme_master_free(image[i].resource);
        }

        /*
         * Ensure counter set correctly to unalloc all slave windows and buffers
         */
        i = SLAVE_MAX + 1;
err_slave:
        while (i > SLAVE_MINOR) {
                i--;
                vme_free_consistent(image[i].resource, image[i].size_buf,
                                    image[i].kern_buf, image[i].pci_buf);
                vme_slave_free(image[i].resource);
        }
err_class:
        cdev_del(vme_user_cdev);
err_char:
        unregister_chrdev_region(MKDEV(VME_MAJOR, 0), VME_DEVS);
err_region:
err_dev:
        return err;
}

static void vme_user_remove(struct vme_dev *vdev)
{
        int i;

        /* Remove sysfs Entries */
        for (i = 0; i < VME_DEVS; i++) {
                mutex_destroy(&image[i].mutex);
                device_destroy(&vme_user_sysfs_class, MKDEV(VME_MAJOR, i));
        }
        class_unregister(&vme_user_sysfs_class);

        for (i = MASTER_MINOR; i < (MASTER_MAX + 1); i++) {
                kfree(image[i].kern_buf);
                vme_master_free(image[i].resource);
        }

        for (i = SLAVE_MINOR; i < (SLAVE_MAX + 1); i++) {
                vme_slave_set(image[i].resource, 0, 0, 0, 0, VME_A32, 0);
                vme_free_consistent(image[i].resource, image[i].size_buf,
                                    image[i].kern_buf, image[i].pci_buf);
                vme_slave_free(image[i].resource);
        }

        /* Unregister device driver */
        cdev_del(vme_user_cdev);

        /* Unregister the major and minor device numbers */
        unregister_chrdev_region(MKDEV(VME_MAJOR, 0), VME_DEVS);
}

static struct vme_driver vme_user_driver = {
        .name = DRIVER_NAME,
        .match = vme_user_match,
        .probe = vme_user_probe,
        .remove = vme_user_remove,
};

static int __init vme_user_init(void)
{
        int retval = 0;

        pr_info("VME User Space Access Driver\n");

        if (bus_num == 0) {
                pr_err("No cards, skipping registration\n");
                retval = -ENODEV;
                goto err_nocard;
        }

        /* Let's start by supporting one bus, we can support more than one
         * in future revisions if that ever becomes necessary.
         */
        if (bus_num > VME_USER_BUS_MAX) {
                pr_err("Driver only able to handle %d buses\n",
                       VME_USER_BUS_MAX);
                bus_num = VME_USER_BUS_MAX;
        }

        /*
         * Here we just register the maximum number of devices we can and
         * leave vme_user_match() to allow only 1 to go through to probe().
         * This way, if we later want to allow multiple user access devices,
         * we just change the code in vme_user_match().
         */
        retval = vme_register_driver(&vme_user_driver, VME_MAX_SLOTS);
        if (retval)
                goto err_reg;

        return retval;

err_reg:
err_nocard:
        return retval;
}

static void __exit vme_user_exit(void)
{
        vme_unregister_driver(&vme_user_driver);
}

MODULE_PARM_DESC(bus, "Enumeration of VMEbus to which the driver is connected");
module_param_array(bus, int, &bus_num, 0000);

MODULE_DESCRIPTION("VME User Space Access Driver");
MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
MODULE_LICENSE("GPL");

module_init(vme_user_init);
module_exit(vme_user_exit);