编写了个videobuf-contig.c以获得物理上连续的大的内存(DMA)

/*
 * helper functions for physically contiguous capture buffers
 *
 * The functions expect the hardware being able to scatter gather
 * (i.e. the buffers are not linear in physical memory, but fragmented
 * into PAGE_SIZE chunks). They also assume the driver does not need
 * to touch the video data.
 *
 * (c) 2009 modified from videobuf-dma-contig by Seen Yang,


 *
 * 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/moduleparam.h>
#include <linux/slab.h>
#include <linux/interrupt.h>

#include <linux/pci.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <asm/page.h>
#include <asm/pgtable.h>

#include <media/videobuf–contig.h>

#define MAGIC_PC_MEM     0x

#define MAGIC_CHECK(is,should)    if (unlikely((is) != (should))) \
    {
printk( “magic mismatch: %x (expected %x)\n”,is,should); BUG(); }

static int debug;
module_param(debug, int, 0644);

MODULE_DESCRIPTION(“helper module to manage video4linux physic continue buffers”);
MODULE_AUTHOR(“Seen Yang,

”
);
MODULE_LICENSE(“GPL”);

#define dprintk(level, fmt, arg...)    if (debug >= level) \
    printk(KERN_DEBUG “vbuf-contig: “ fmt , ## arg)

struct videobuf_contig_memory
{

    u32 magic;
    dma_addr_t paddr;
    void                *vaddr;
    u32                    size;
};

/* Allocate physic continue memory for buffers */
static void *malloc_contig(u32 buf_size)
{

    void *mem = 0;
    u32 size = PAGE_SIZE << (get_order(buf_size));

    mem = (void *)__get_dma_pages(GFP_KERNEL,
                                 get_order(buf_size));
    if (mem) {

        unsigned long adr = (unsigned long)mem;
        while (size > 0) {

            SetPageReserved(virt_to_page(adr));
            adr += PAGE_SIZE;
            size –= PAGE_SIZE;
        }
    } else
        printk( “dma memory can’t be alloced!!\n”);

    return mem;
}

/* Free memory for buffers */
static void free_contig(void *addr, u32 buf_size)
{

    u32 size, adr;

    if (!addr)
        return;
    adr = (u32)addr;
    size = PAGE_SIZE << (get_order(buf_size));
    while (size > 0) {

        ClearPageReserved(virt_to_page(adr));
        adr += PAGE_SIZE;
        size –= PAGE_SIZE;
    }
    free_pages((u32)addr, get_order(buf_size));
}

/*/

static void
videobuf_vm_open(struct vm_area_struct *vma)
{

    struct videobuf_mapping *map = vma–>vm_private_data;

    dprintk(2,“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;

    dprintk(2,“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_contig_memory *mem;

        dprintk(1, “munmap %p q=%p\n”, map, q);
        mutex_lock(&q–>vb_lock);

        /* 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_PC_MEM);

                dprintk(1, “%s: buf[%d] freeing (%d)\n”,
                    __func__, i, mem–>paddr);

                free_contig(mem–>vaddr, mem–>size);
                mem–>paddr = 0;
                mem–>vaddr = NULL;
            }

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

        kfree(map);

        mutex_unlock(&q–>vb_lock);
    }

    return;
}

static struct vm_operations_struct videobuf_vm_ops =
{

    .open = videobuf_vm_open,
    .close = videobuf_vm_close,
};

/* ———————————————————————
 * contig handlers for the generic methods
 */

/* Allocated area consists on 3 parts:
    struct video_buffer
    struct

_buffer (cx88_buffer, saa7134_buf, …)

    struct videobuf_dma_sg_memory
 */

static void *__videobuf_alloc(size_t size)
{

    struct videobuf_contig_memory *mem;
    struct videobuf_buffer *vb;

    vb = kzalloc(size+sizeof(*mem),GFP_KERNEL);

    mem = vb–>priv = ((char *)vb)+size;
    mem–>magic=MAGIC_PC_MEM;

    dprintk(1,“%s: allocated at %p(%ld+%ld) & %p(%ld)\n”,
        __func__,vb,(long)sizeof(*vb),(long)size–sizeof(*vb),
        mem,(long)sizeof(*mem));

    return vb;
}

static int __videobuf_iolock (struct videobuf_queue* q,
             struct videobuf_buffer *vb,
             struct v4l2_framebuffer *fbuf)
{

    struct videobuf_contig_memory *mem = vb–>priv;

    BUG_ON(!mem);

    MAGIC_CHECK(mem–>magic, MAGIC_PC_MEM);

    switch (vb–>memory) {

    case V4L2_MEMORY_MMAP:
        dprintk(1, “%s memory method MMAP\n”, __func__);

        /* All handling should be done by __videobuf_mmap_mapper() */
        if (!mem–>paddr) {

            printk(KERN_ERR “memory is not alloced/mmapped.\n”);
            return –EINVAL;
        }
        break;
    case V4L2_MEMORY_USERPTR:

        dprintk(1, “%s memory method USERPTR\n”, __func__);

        if (vb–>baddr) {

            printk(KERN_ERR “USERPTR is currently not supported\n”);
            return –EINVAL;
        }

        /* The only USERPTR currently supported is the one needed for
         read() method.
         */


        
        mem–>size = PAGE_ALIGN(vb–>size);
        mem–>vaddr = malloc_contig(mem–>size);
        if (!mem–>vaddr) {

            printk(KERN_ERR “malloc_contig (%d pages) failed\n”, mem–>size);
            return –ENOMEM;
        }
        mem–>paddr = virt_to_phys(mem–>vaddr);
        
        dprintk(1, “malloc_contig is at addr %d (%d pages)\n”,
            mem–>paddr, mem–>size);

        break;
    case V4L2_MEMORY_OVERLAY:
    default:
        dprintk(1, “%s memory method OVERLAY/unknown\n”, __func__);

        /* Currently, doesn’t support V4L2_MEMORY_OVERLAY */
        printk(KERN_ERR “Memory method currently unsupported.\n”);
        return –EINVAL;
    }

    return 0;
}

static int __videobuf_sync(struct videobuf_queue *q,
             struct videobuf_buffer *buf)
{

    return 0;
}

static int __videobuf_mmap_free(struct videobuf_queue *q)
{

    unsigned int i;

    dprintk(1, “%s\n”, __func__);
    for (i = 0; i < VIDEO_MAX_FRAME; i++) {

        if (q–>bufs[i]) {

            if (q–>bufs[i]–>map)
                return –EBUSY;
        }
    }

    return 0;
}

static int __videobuf_mmap_mapper(struct videobuf_queue *q,
             struct vm_area_struct *vma)
{

    struct videobuf_contig_memory *mem;
    struct videobuf_mapping *map;
    unsigned int first;
    int retval, size;
    unsigned long offset = vma–>vm_pgoff << PAGE_SHIFT;

    dprintk(1, “%s\n”, __func__);
    if (!(vma–>vm_flags & VM_WRITE) || !(vma–>vm_flags & VM_SHARED))
        return –EINVAL;

    /* look for first buffer to map */
    for (first = 0; first < VIDEO_MAX_FRAME; first++) {

        if (NULL == q–>bufs[first])
            continue;

        if (V4L2_MEMORY_MMAP != q–>bufs[first]–>memory)
            continue;
        if (q–>bufs[first]–>boff == offset)
            break;
    }
    if (VIDEO_MAX_FRAME == first) {

        dprintk(1,“mmap app bug: invalid user space offset [offset=0x%lx]\n”,
            (vma–>vm_pgoff << PAGE_SHIFT));
        return –EINVAL;
    }

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

    q–>bufs[first]–>map = map;
    map–>start = vma–>vm_start;
    map–>end = vma–>vm_end;
    map–>q = q;

    q–>bufs[first]–>baddr = vma–>vm_start;

    mem = q–>bufs[first]–>priv;
    BUG_ON(!mem);
    MAGIC_CHECK(mem–>magic, MAGIC_PC_MEM);

    mem–>size = PAGE_ALIGN(q–>bufs[first]–>bsize);
    mem–>vaddr = malloc_contig(mem–>size);
    if (!mem–>vaddr) {

        printk(KERN_ERR “malloc_contig (%d size) failed\n”, mem–>size);
        goto error;
    }
    mem–>paddr = virt_to_phys(mem–>vaddr);
    
    dprintk(1, “malloc_contig is at addr %i (%d size)\n”,
        mem–>paddr, mem–>size);

    size = vma–>vm_end – vma–>vm_start;
    size = (size < mem–>size) ? size : mem–>size;

    /* Try to remap memory */
    vma–>vm_page_prot = pgprot_writecombine(vma–>vm_page_prot);
    retval = remap_pfn_range(vma, vma–>vm_start,
                             mem–>paddr >> PAGE_SHIFT,
                             size, vma–>vm_page_prot);
    if (retval < 0) {

        printk(KERN_ERR “mmap: remap failed with error %d. “, retval);
        free_contig(mem–>vaddr, mem–>size);
        goto error;
    }

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

    dprintk(1,“mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n”,
        map, q, vma–>vm_start, vma–>vm_end,
        (long int) q–>bufs[first]–>bsize,
        vma–>vm_pgoff, first);

    videobuf_vm_open(vma);

    return 0;

error:
    mem = NULL;
    kfree(map);
    return –ENOMEM;
}

static int __videobuf_copy_to_user ( struct videobuf_queue *q,
                char __user *data, size_t count,
                int nonblocking )
{

    struct videobuf_contig_memory *mem = q–>read_buf–>priv;
    void *vaddr;

    BUG_ON(!mem);
    MAGIC_CHECK(mem–>magic, MAGIC_PC_MEM);
    BUG_ON(!mem–>vaddr);

    /* copy to userspace */
    if (count > q–>read_buf–>size – q–>read_off)
        count = q–>read_buf–>size – q–>read_off;

    vaddr = mem–>vaddr;

    if (copy_to_user(data, vaddr + q–>read_off, count))
        return –EFAULT;

    return count;
}

static int __videobuf_copy_stream ( struct videobuf_queue *q,
                char __user *data, size_t count, size_t pos,
                int vbihack, int nonblocking )
{

    unsigned int *fc;
    struct videobuf_contig_memory *mem=q–>read_buf–>priv;
    BUG_ON (!mem);
    MAGIC_CHECK(mem–>magic,MAGIC_PC_MEM);

    if (vbihack) {

        /* dirty, undocumented hack — pass the frame counter
            * within the last four bytes of each vbi data block.
            * We need that one to maintain backward compatibility
            * to all vbi decoding software out there … */



        fc = (unsigned int*)mem–>vaddr;
        fc += (q–>read_buf–>size>>2) –1;
        *fc = q–>read_buf–>field_count >> 1;
        dprintk(1,“vbihack: %d\n”,*fc);
    }

    /* copy stuff using the common method */
    count = __videobuf_copy_to_user (q, data, count, nonblocking);

    if ( (count==–EFAULT) && (0 == pos) )
        return –EFAULT;

    return count;
}

static void *__videobuf_to_vmalloc(struct videobuf_buffer *buf)
{

    struct videobuf_contig_memory *mem = buf–>priv;

    BUG_ON(!mem);
    MAGIC_CHECK(mem–>magic, MAGIC_PC_MEM);

    return mem–>vaddr;
}

static struct videobuf_qtype_ops qops = {

    .magic = MAGIC_QTYPE_OPS,

    .alloc = __videobuf_alloc,
    .iolock = __videobuf_iolock,
    .sync = __videobuf_sync,
    .mmap_free = __videobuf_mmap_free,
    .mmap_mapper = __videobuf_mmap_mapper,
    .video_copy_to_user = __videobuf_copy_to_user,
    .copy_stream = __videobuf_copy_stream,
    .vmalloc = __videobuf_to_vmalloc,
};

void videobuf_queue_contig_init(struct videobuf_queue* q,
             struct videobuf_queue_ops *ops,
             void *dev,
             spinlock_t *irqlock,
             enum v4l2_buf_type type,
             enum v4l2_field field,
             unsigned int msize,
             void *priv)
{

    videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
                 priv, &qops);
}

EXPORT_SYMBOL_GPL(videobuf_queue_contig_init);

u32 videobuf_to_contig (struct videobuf_buffer *buf)
{

    struct videobuf_contig_memory *mem=buf–>priv;
    BUG_ON (!mem);
    MAGIC_CHECK(mem–>magic,MAGIC_PC_MEM);

    return mem–>paddr;
}
EXPORT_SYMBOL_GPL(videobuf_to_contig);

void videobuf_contig_free (struct videobuf_buffer *buf)
{

    struct videobuf_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) || !buf–>baddr)
        return;
    
    if (!mem)
        return;

    MAGIC_CHECK(mem–>magic, MAGIC_PC_MEM);

    free_contig(mem–>vaddr, mem–>size);
    mem–>paddr = 0;
    mem–>vaddr = NULL;

    return;
}
EXPORT_SYMBOL_GPL(videobuf_contig_free);