// SPDX-License-Identifier: GPL-2.0
/*
 * Framework for userspace DMA-BUF allocations
 *
 * Copyright (C) 2011 Google, Inc.
 * Copyright (C) 2019 Linaro Ltd.
 */

#include <linux/cdev.h>
#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/dma-buf.h>
#include <linux/err.h>
#include <linux/xarray.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/dma-heap.h>
#include <uapi/linux/dma-heap.h>

#define DEVNAME "dma_heap"

#define NUM_HEAP_MINORS 128

/**
 * struct dma_heap - represents a dmabuf heap in the system
 * @name:               used for debugging/device-node name
 * @ops:                ops struct for this heap
 * @heap_devt           heap device node
 * @list                list head connecting to list of heaps
 * @heap_cdev           heap char device
 *
 * Represents a heap of memory from which buffers can be made.
 */
struct dma_heap {
        const char *name;
        const struct dma_heap_ops *ops;
        void *priv;
        dev_t heap_devt;
        struct list_head list;
        struct cdev heap_cdev;
};

static LIST_HEAD(heap_list);
static DEFINE_MUTEX(heap_list_lock);
static dev_t dma_heap_devt;
static struct class *dma_heap_class;
static DEFINE_XARRAY_ALLOC(dma_heap_minors);

static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
                                 unsigned int fd_flags,
                                 unsigned int heap_flags)
{
        /*
         * Allocations from all heaps have to begin
         * and end on page boundaries.
         */
        len = PAGE_ALIGN(len);
        if (!len)
                return -EINVAL;

        return heap->ops->allocate(heap, len, fd_flags, heap_flags);
}

static int dma_heap_open(struct inode *inode, struct file *file)
{
        struct dma_heap *heap;

        heap = xa_load(&dma_heap_minors, iminor(inode));
        if (!heap) {
                pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
                return -ENODEV;
        }

        /* instance data as context */
        file->private_data = heap;
        nonseekable_open(inode, file);

        return 0;
}

static long dma_heap_ioctl_allocate(struct file *file, void *data)
{
        struct dma_heap_allocation_data *heap_allocation = data;
        struct dma_heap *heap = file->private_data;
        int fd;

        if (heap_allocation->fd)
                return -EINVAL;

        if (heap_allocation->fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
                return -EINVAL;

        if (heap_allocation->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
                return -EINVAL;

        fd = dma_heap_buffer_alloc(heap, heap_allocation->len,
                                   heap_allocation->fd_flags,
                                   heap_allocation->heap_flags);
        if (fd < 0)
                return fd;

        heap_allocation->fd = fd;

        return 0;
}

static unsigned int dma_heap_ioctl_cmds[] = {
        DMA_HEAP_IOCTL_ALLOC,
};

static long dma_heap_ioctl(struct file *file, unsigned int ucmd,
                           unsigned long arg)
{
        char stack_kdata[128];
        char *kdata = stack_kdata;
        unsigned int kcmd;
        unsigned int in_size, out_size, drv_size, ksize;
        int nr = _IOC_NR(ucmd);
        int ret = 0;

        if (nr >= ARRAY_SIZE(dma_heap_ioctl_cmds))
                return -EINVAL;

        /* Get the kernel ioctl cmd that matches */
        kcmd = dma_heap_ioctl_cmds[nr];

        /* Figure out the delta between user cmd size and kernel cmd size */
        drv_size = _IOC_SIZE(kcmd);
        out_size = _IOC_SIZE(ucmd);
        in_size = out_size;
        if ((ucmd & kcmd & IOC_IN) == 0)
                in_size = 0;
        if ((ucmd & kcmd & IOC_OUT) == 0)
                out_size = 0;
        ksize = max(max(in_size, out_size), drv_size);

        /* If necessary, allocate buffer for ioctl argument */
        if (ksize > sizeof(stack_kdata)) {
                kdata = kmalloc(ksize, GFP_KERNEL);
                if (!kdata)
                        return -ENOMEM;
        }

        if (copy_from_user(kdata, (void __user *)arg, in_size) != 0) {
                ret = -EFAULT;
                goto err;
        }

        /* zero out any difference between the kernel/user structure size */
        if (ksize > in_size)
                memset(kdata + in_size, 0, ksize - in_size);

        switch (kcmd) {
        case DMA_HEAP_IOCTL_ALLOC:
                ret = dma_heap_ioctl_allocate(file, kdata);
                break;
        default:
                ret = -ENOTTY;
                goto err;
        }

        if (copy_to_user((void __user *)arg, kdata, out_size) != 0)
                ret = -EFAULT;
err:
        if (kdata != stack_kdata)
                kfree(kdata);
        return ret;
}

static const struct file_operations dma_heap_fops = {
        .owner          = THIS_MODULE,
        .open           = dma_heap_open,
        .unlocked_ioctl = dma_heap_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = dma_heap_ioctl,
#endif
};

/**
 * dma_heap_get_drvdata() - get per-subdriver data for the heap
 * @heap: DMA-Heap to retrieve private data for
 *
 * Returns:
 * The per-subdriver data for the heap.
 */
void *dma_heap_get_drvdata(struct dma_heap *heap)
{
        return heap->priv;
}

struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
{
        struct dma_heap *heap, *h, *err_ret;
        struct device *dev_ret;
        unsigned int minor;
        int ret;

        if (!exp_info->name || !strcmp(exp_info->name, "")) {
                pr_err("dma_heap: Cannot add heap without a name\n");
                return ERR_PTR(-EINVAL);
        }

        if (!exp_info->ops || !exp_info->ops->allocate) {
                pr_err("dma_heap: Cannot add heap with invalid ops struct\n");
                return ERR_PTR(-EINVAL);
        }

        /* check the name is unique */
        mutex_lock(&heap_list_lock);
        list_for_each_entry(h, &heap_list, list) {
                if (!strcmp(h->name, exp_info->name)) {
                        mutex_unlock(&heap_list_lock);
                        pr_err("dma_heap: Already registered heap named %s\n",
                               exp_info->name);
                        return ERR_PTR(-EINVAL);
                }
        }
        mutex_unlock(&heap_list_lock);

        heap = kzalloc(sizeof(*heap), GFP_KERNEL);
        if (!heap)
                return ERR_PTR(-ENOMEM);

        heap->name = exp_info->name;
        heap->ops = exp_info->ops;
        heap->priv = exp_info->priv;

        /* Find unused minor number */
        ret = xa_alloc(&dma_heap_minors, &minor, heap,
                       XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
        if (ret < 0) {
                pr_err("dma_heap: Unable to get minor number for heap\n");
                err_ret = ERR_PTR(ret);
                goto err0;
        }

        /* Create device */
        heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), minor);

        cdev_init(&heap->heap_cdev, &dma_heap_fops);
        ret = cdev_add(&heap->heap_cdev, heap->heap_devt, 1);
        if (ret < 0) {
                pr_err("dma_heap: Unable to add char device\n");
                err_ret = ERR_PTR(ret);
                goto err1;
        }

        dev_ret = device_create(dma_heap_class,
                                NULL,
                                heap->heap_devt,
                                NULL,
                                heap->name);
        if (IS_ERR(dev_ret)) {
                pr_err("dma_heap: Unable to create device\n");
                err_ret = ERR_CAST(dev_ret);
                goto err2;
        }
        /* Add heap to the list */
        mutex_lock(&heap_list_lock);
        list_add(&heap->list, &heap_list);
        mutex_unlock(&heap_list_lock);

        return heap;

err2:
        cdev_del(&heap->heap_cdev);
err1:
        xa_erase(&dma_heap_minors, minor);
err0:
        kfree(heap);
        return err_ret;
}

static char *dma_heap_devnode(struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "dma_heap/%s", dev_name(dev));
}

static int dma_heap_init(void)
{
        int ret;

        ret = alloc_chrdev_region(&dma_heap_devt, 0, NUM_HEAP_MINORS, DEVNAME);
        if (ret)
                return ret;

        dma_heap_class = class_create(THIS_MODULE, DEVNAME);
        if (IS_ERR(dma_heap_class)) {
                unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
                return PTR_ERR(dma_heap_class);
        }
        dma_heap_class->devnode = dma_heap_devnode;

        return 0;
}
subsys_initcall(dma_heap_init);