/*
 * videobuf2-vmalloc.c - vmalloc memory allocator for videobuf2
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <pawel@osciak.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <media/videobuf2-core.h>
#include <media/videobuf2-memops.h>

struct vb2_vmalloc_buf {
        void                            *vaddr;
        struct page                     **pages;
        int                             write;
        unsigned long                   size;
        unsigned int                    n_pages;
        atomic_t                        refcount;
        struct vb2_vmarea_handler       handler;
};

static void vb2_vmalloc_put(void *buf_priv);

static void *vb2_vmalloc_alloc(void *alloc_ctx, unsigned long size)
{
        struct vb2_vmalloc_buf *buf;

        buf = kzalloc(sizeof(*buf), GFP_KERNEL);
        if (!buf)
                return NULL;

        buf->size = size;
        buf->vaddr = vmalloc_user(buf->size);
        buf->handler.refcount = &buf->refcount;
        buf->handler.put = vb2_vmalloc_put;
        buf->handler.arg = buf;

        if (!buf->vaddr) {
                pr_debug("vmalloc of size %ld failed\n", buf->size);
                kfree(buf);
                return NULL;
        }

        atomic_inc(&buf->refcount);
        return buf;
}

static void vb2_vmalloc_put(void *buf_priv)
{
        struct vb2_vmalloc_buf *buf = buf_priv;

        if (atomic_dec_and_test(&buf->refcount)) {
                vfree(buf->vaddr);
                kfree(buf);
        }
}

static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
                                     unsigned long size, int write)
{
        struct vb2_vmalloc_buf *buf;
        unsigned long first, last;
        int n_pages, offset;

        buf = kzalloc(sizeof(*buf), GFP_KERNEL);
        if (!buf)
                return NULL;

        buf->write = write;
        offset = vaddr & ~PAGE_MASK;
        buf->size = size;

        first = vaddr >> PAGE_SHIFT;
        last  = (vaddr + size - 1) >> PAGE_SHIFT;
        buf->n_pages = last - first + 1;
        buf->pages = kzalloc(buf->n_pages * sizeof(struct page *), GFP_KERNEL);
        if (!buf->pages)
                goto fail_pages_array_alloc;

        /* current->mm->mmap_sem is taken by videobuf2 core */
        n_pages = get_user_pages(current, current->mm, vaddr & PAGE_MASK,
                                 buf->n_pages, write, 1, /* force */
                                 buf->pages, NULL);
        if (n_pages != buf->n_pages)
                goto fail_get_user_pages;

        buf->vaddr = vm_map_ram(buf->pages, buf->n_pages, -1, PAGE_KERNEL);
        if (!buf->vaddr)
                goto fail_get_user_pages;

        buf->vaddr += offset;
        return buf;

fail_get_user_pages:
        pr_debug("get_user_pages requested/got: %d/%d]\n", n_pages,
                 buf->n_pages);
        while (--n_pages >= 0)
                put_page(buf->pages[n_pages]);
        kfree(buf->pages);

fail_pages_array_alloc:
        kfree(buf);

        return NULL;
}

static void vb2_vmalloc_put_userptr(void *buf_priv)
{
        struct vb2_vmalloc_buf *buf = buf_priv;
        unsigned long vaddr = (unsigned long)buf->vaddr & PAGE_MASK;
        unsigned int i;

        if (vaddr)
                vm_unmap_ram((void *)vaddr, buf->n_pages);
        for (i = 0; i < buf->n_pages; ++i) {
                if (buf->write)
                        set_page_dirty_lock(buf->pages[i]);
                put_page(buf->pages[i]);
        }
        kfree(buf->pages);
        kfree(buf);
}

static void *vb2_vmalloc_vaddr(void *buf_priv)
{
        struct vb2_vmalloc_buf *buf = buf_priv;

        if (!buf->vaddr) {
                pr_err("Address of an unallocated plane requested "
                       "or cannot map user pointer\n");
                return NULL;
        }

        return buf->vaddr;
}

static unsigned int vb2_vmalloc_num_users(void *buf_priv)
{
        struct vb2_vmalloc_buf *buf = buf_priv;
        return atomic_read(&buf->refcount);
}

static int vb2_vmalloc_mmap(void *buf_priv, struct vm_area_struct *vma)
{
        struct vb2_vmalloc_buf *buf = buf_priv;
        int ret;

        if (!buf) {
                pr_err("No memory to map\n");
                return -EINVAL;
        }

        ret = remap_vmalloc_range(vma, buf->vaddr, 0);
        if (ret) {
                pr_err("Remapping vmalloc memory, error: %d\n", ret);
                return ret;
        }

        /*
         * Make sure that vm_areas for 2 buffers won't be merged together
         */
        vma->vm_flags           |= VM_DONTEXPAND;

        /*
         * Use common vm_area operations to track buffer refcount.
         */
        vma->vm_private_data    = &buf->handler;
        vma->vm_ops             = &vb2_common_vm_ops;

        vma->vm_ops->open(vma);

        return 0;
}

const struct vb2_mem_ops vb2_vmalloc_memops = {
        .alloc          = vb2_vmalloc_alloc,
        .put            = vb2_vmalloc_put,
        .get_userptr    = vb2_vmalloc_get_userptr,
        .put_userptr    = vb2_vmalloc_put_userptr,
        .vaddr          = vb2_vmalloc_vaddr,
        .mmap           = vb2_vmalloc_mmap,
        .num_users      = vb2_vmalloc_num_users,
};
EXPORT_SYMBOL_GPL(vb2_vmalloc_memops);

MODULE_DESCRIPTION("vmalloc memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
MODULE_LICENSE("GPL");