/*
 * helper functions for physically contiguous capture buffers
 *
 * The functions support hardware lacking scatter gather support
 * (i.e. the buffers must be linear in physical memory)
 *
 * Copyright (c) 2008 Magnus Damm
 *
 * Based on videobuf-vmalloc.c,
 * (c) 2007 Mauro Carvalho Chehab, <mchehab@infradead.org>
 *
 * 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; either version 2
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/dma-mapping.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <media/videobuf-dma-contig.h>

struct videobuf_dma_contig_memory {
        u32 magic;
        void *vaddr;
        dma_addr_t dma_handle;
        unsigned long size;
};

#define MAGIC_DC_MEM 0x0733ac61
#define MAGIC_CHECK(is, should)                                             \
        if (unlikely((is) != (should))) {                                   \
                pr_err("magic mismatch: %x expected %x\n", (is), (should)); \
                BUG();                                                      \
        }

static int __videobuf_dc_alloc(struct device *dev,
                               struct videobuf_dma_contig_memory *mem,
                               unsigned long size, gfp_t flags)
{
        mem->size = size;
        mem->vaddr = dma_alloc_coherent(dev, mem->size,
                                        &mem->dma_handle, flags);

        if (!mem->vaddr) {
                dev_err(dev, "memory alloc size %ld failed\n", mem->size);
                return -ENOMEM;
        }

        dev_dbg(dev, "dma mapped data is at %p (%ld)\n", mem->vaddr, mem->size);

        return 0;
}

static void __videobuf_dc_free(struct device *dev,
                               struct videobuf_dma_contig_memory *mem)
{
        dma_free_coherent(dev, mem->size, mem->vaddr, mem->dma_handle);

        mem->vaddr = NULL;
}

static void videobuf_vm_open(struct vm_area_struct *vma)
{
        struct videobuf_mapping *map = vma->vm_private_data;

        dev_dbg(map->q->dev, "vm_open %p [count=%u,vma=%08lx-%08lx]\n",
                map, map->count, vma->vm_start, vma->vm_end);

        map->count++;
}

static void videobuf_vm_close(struct vm_area_struct *vma)
{
        struct videobuf_mapping *map = vma->vm_private_data;
        struct videobuf_queue *q = map->q;
        int i;

        dev_dbg(q->dev, "vm_close %p [count=%u,vma=%08lx-%08lx]\n",
                map, map->count, vma->vm_start, vma->vm_end);

        map->count--;
        if (0 == map->count) {
                struct videobuf_dma_contig_memory *mem;

                dev_dbg(q->dev, "munmap %p q=%p\n", map, q);
                videobuf_queue_lock(q);

                /* We need first to cancel streams, before unmapping */
                if (q->streaming)
                        videobuf_queue_cancel(q);

                for (i = 0; i < VIDEO_MAX_FRAME; i++) {
                        if (NULL == q->bufs[i])
                                continue;

                        if (q->bufs[i]->map != map)
                                continue;

                        mem = q->bufs[i]->priv;
                        if (mem) {
                                /* This callback is called only if kernel has
                                   allocated memory and this memory is mmapped.
                                   In this case, memory should be freed,
                                   in order to do memory unmap.
                                 */

                                MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

                                /* vfree is not atomic - can't be
                                   called with IRQ's disabled
                                 */
                                dev_dbg(q->dev, "buf[%d] freeing %p\n",
                                        i, mem->vaddr);

                                __videobuf_dc_free(q->dev, mem);
                                mem->vaddr = NULL;
                        }

                        q->bufs[i]->map = NULL;
                        q->bufs[i]->baddr = 0;
                }

                kfree(map);

                videobuf_queue_unlock(q);
        }
}

static const struct vm_operations_struct videobuf_vm_ops = {
        .open   = videobuf_vm_open,
        .close  = videobuf_vm_close,
};

/**
 * videobuf_dma_contig_user_put() - reset pointer to user space buffer
 * @mem: per-buffer private videobuf-dma-contig data
 *
 * This function resets the user space pointer
 */
static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem)
{
        mem->dma_handle = 0;
        mem->size = 0;
}

/**
 * videobuf_dma_contig_user_get() - setup user space memory pointer
 * @mem: per-buffer private videobuf-dma-contig data
 * @vb: video buffer to map
 *
 * This function validates and sets up a pointer to user space memory.
 * Only physically contiguous pfn-mapped memory is accepted.
 *
 * Returns 0 if successful.
 */
static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
                                        struct videobuf_buffer *vb)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long prev_pfn, this_pfn;
        unsigned long pages_done, user_address;
        unsigned int offset;
        int ret;

        offset = vb->baddr & ~PAGE_MASK;
        mem->size = PAGE_ALIGN(vb->size + offset);
        ret = -EINVAL;

        down_read(&mm->mmap_sem);

        vma = find_vma(mm, vb->baddr);
        if (!vma)
                goto out_up;

        if ((vb->baddr + mem->size) > vma->vm_end)
                goto out_up;

        pages_done = 0;
        prev_pfn = 0; /* kill warning */
        user_address = vb->baddr;

        while (pages_done < (mem->size >> PAGE_SHIFT)) {
                ret = follow_pfn(vma, user_address, &this_pfn);
                if (ret)
                        break;

                if (pages_done == 0)
                        mem->dma_handle = (this_pfn << PAGE_SHIFT) + offset;
                else if (this_pfn != (prev_pfn + 1))
                        ret = -EFAULT;

                if (ret)
                        break;

                prev_pfn = this_pfn;
                user_address += PAGE_SIZE;
                pages_done++;
        }

out_up:
        up_read(&current->mm->mmap_sem);

        return ret;
}

static struct videobuf_buffer *__videobuf_alloc(size_t size)
{
        struct videobuf_dma_contig_memory *mem;
        struct videobuf_buffer *vb;

        vb = kzalloc(size + sizeof(*mem), GFP_KERNEL);
        if (vb) {
                vb->priv = ((char *)vb) + size;
                mem = vb->priv;
                mem->magic = MAGIC_DC_MEM;
        }

        return vb;
}

static void *__videobuf_to_vaddr(struct videobuf_buffer *buf)
{
        struct videobuf_dma_contig_memory *mem = buf->priv;

        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

        return mem->vaddr;
}

static int __videobuf_iolock(struct videobuf_queue *q,
                             struct videobuf_buffer *vb,
                             struct v4l2_framebuffer *fbuf)
{
        struct videobuf_dma_contig_memory *mem = vb->priv;

        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

        switch (vb->memory) {
        case V4L2_MEMORY_MMAP:
                dev_dbg(q->dev, "%s memory method MMAP\n", __func__);

                /* All handling should be done by __videobuf_mmap_mapper() */
                if (!mem->vaddr) {
                        dev_err(q->dev, "memory is not alloced/mmapped.\n");
                        return -EINVAL;
                }
                break;
        case V4L2_MEMORY_USERPTR:
                dev_dbg(q->dev, "%s memory method USERPTR\n", __func__);

                /* handle pointer from user space */
                if (vb->baddr)
                        return videobuf_dma_contig_user_get(mem, vb);

                /* allocate memory for the read() method */
                if (__videobuf_dc_alloc(q->dev, mem, PAGE_ALIGN(vb->size),
                                        GFP_KERNEL))
                        return -ENOMEM;
                break;
        case V4L2_MEMORY_OVERLAY:
        default:
                dev_dbg(q->dev, "%s memory method OVERLAY/unknown\n", __func__);
                return -EINVAL;
        }

        return 0;
}

static int __videobuf_mmap_mapper(struct videobuf_queue *q,
                                  struct videobuf_buffer *buf,
                                  struct vm_area_struct *vma)
{
        struct videobuf_dma_contig_memory *mem;
        struct videobuf_mapping *map;
        int retval;
        unsigned long size;

        dev_dbg(q->dev, "%s\n", __func__);

        /* create mapping + update buffer list */
        map = kzalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
        if (!map)
                return -ENOMEM;

        buf->map = map;
        map->q = q;

        buf->baddr = vma->vm_start;

        mem = buf->priv;
        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

        if (__videobuf_dc_alloc(q->dev, mem, PAGE_ALIGN(buf->bsize),
                                GFP_KERNEL | __GFP_COMP))
                goto error;

        /* Try to remap memory */
        size = vma->vm_end - vma->vm_start;
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        /* the "vm_pgoff" is just used in v4l2 to find the
         * corresponding buffer data structure which is allocated
         * earlier and it does not mean the offset from the physical
         * buffer start address as usual. So set it to 0 to pass
         * the sanity check in vm_iomap_memory().
         */
        vma->vm_pgoff = 0;

        retval = vm_iomap_memory(vma, mem->dma_handle, size);
        if (retval) {
                dev_err(q->dev, "mmap: remap failed with error %d. ",
                        retval);
                dma_free_coherent(q->dev, mem->size,
                                  mem->vaddr, mem->dma_handle);
                goto error;
        }

        vma->vm_ops = &videobuf_vm_ops;
        vma->vm_flags |= VM_DONTEXPAND;
        vma->vm_private_data = map;

        dev_dbg(q->dev, "mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n",
                map, q, vma->vm_start, vma->vm_end,
                (long int)buf->bsize, vma->vm_pgoff, buf->i);

        videobuf_vm_open(vma);

        return 0;

error:
        kfree(map);
        return -ENOMEM;
}

static struct videobuf_qtype_ops qops = {
        .magic          = MAGIC_QTYPE_OPS,
        .alloc_vb       = __videobuf_alloc,
        .iolock         = __videobuf_iolock,
        .mmap_mapper    = __videobuf_mmap_mapper,
        .vaddr          = __videobuf_to_vaddr,
};

void videobuf_queue_dma_contig_init(struct videobuf_queue *q,
                                    const struct videobuf_queue_ops *ops,
                                    struct device *dev,
                                    spinlock_t *irqlock,
                                    enum v4l2_buf_type type,
                                    enum v4l2_field field,
                                    unsigned int msize,
                                    void *priv,
                                    struct mutex *ext_lock)
{
        videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
                                 priv, &qops, ext_lock);
}
EXPORT_SYMBOL_GPL(videobuf_queue_dma_contig_init);

dma_addr_t videobuf_to_dma_contig(struct videobuf_buffer *buf)
{
        struct videobuf_dma_contig_memory *mem = buf->priv;

        BUG_ON(!mem);
        MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

        return mem->dma_handle;
}
EXPORT_SYMBOL_GPL(videobuf_to_dma_contig);

void videobuf_dma_contig_free(struct videobuf_queue *q,
                              struct videobuf_buffer *buf)
{
        struct videobuf_dma_contig_memory *mem = buf->priv;

        /* mmapped memory can't be freed here, otherwise mmapped region
           would be released, while still needed. In this case, the memory
           release should happen inside videobuf_vm_close().
           So, it should free memory only if the memory were allocated for
           read() operation.
         */
        if (buf->memory != V4L2_MEMORY_USERPTR)
                return;

        if (!mem)
                return;

        MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

        /* handle user space pointer case */
        if (buf->baddr) {
                videobuf_dma_contig_user_put(mem);
                return;
        }

        /* read() method */
        if (mem->vaddr) {
                __videobuf_dc_free(q->dev, mem);
                mem->vaddr = NULL;
        }
}
EXPORT_SYMBOL_GPL(videobuf_dma_contig_free);

MODULE_DESCRIPTION("helper module to manage video4linux dma contig buffers");
MODULE_AUTHOR("Magnus Damm");
MODULE_LICENSE("GPL");