videobuf-dma-sg.c

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/*
 * helper functions for SG DMA video4linux 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) 2007 Mauro Carvalho Chehab, <[email protected]>
 *
 * Highly based on video-buf written originally by:
 * (c) 2001,02 Gerd Knorr <[email protected]>
 * (c) 2006 Mauro Carvalho Chehab, <[email protected]>
 * (c) 2006 Ted Walther and John Sokol
 *
 * 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/sched.h>
#include <linux/slab.h>
#include <linux/interrupt.h>

#include <linux/dma-mapping.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/scatterlist.h>
#include <asm/page.h>
#include <asm/pgtable.h>

#include <media/videobuf-dma-sg.h>

#define MAGIC_DMABUF 0x19721112
#define MAGIC_SG_MEM 0x17890714

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

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

MODULE_DESCRIPTION("helper module to manage video4linux dma sg buffers");
MODULE_AUTHOR("Mauro Carvalho Chehab <[email protected]>");
MODULE_LICENSE("GPL");

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

/* --------------------------------------------------------------------- */

/*
 * Return a scatterlist for some page-aligned vmalloc()'ed memory
 * block (NULL on errors).  Memory for the scatterlist is allocated
 * using kmalloc.  The caller must free the memory.
 */
static struct scatterlist *videobuf_vmalloc_to_sg(unsigned char *virt,
                          int nr_pages)
{
    struct scatterlist *sglist;
    struct page *pg;
    int i;

    sglist = vzalloc(nr_pages * sizeof(*sglist));
    if (NULL == sglist)
        return NULL;
    sg_init_table(sglist, nr_pages);
    for (i = 0; i < nr_pages; i++, virt += PAGE_SIZE) {
        pg = vmalloc_to_page(virt);
        if (NULL == pg)
            goto err;
        BUG_ON(PageHighMem(pg));
        sg_set_page(&sglist[i], pg, PAGE_SIZE, 0);
    }
    return sglist;

err:
    vfree(sglist);
    return NULL;
}

/*
 * Return a scatterlist for a an array of userpages (NULL on errors).
 * Memory for the scatterlist is allocated using kmalloc.  The caller
 * must free the memory.
 */
static struct scatterlist *videobuf_pages_to_sg(struct page **pages,
                    int nr_pages, int offset, size_t size)
{
    struct scatterlist *sglist;
    int i;

    if (NULL == pages[0])
        return NULL;
    sglist = vmalloc(nr_pages * sizeof(*sglist));
    if (NULL == sglist)
        return NULL;
    sg_init_table(sglist, nr_pages);

    if (PageHighMem(pages[0]))
        /* DMA to highmem pages might not work */
        goto highmem;
    sg_set_page(&sglist[0], pages[0],
            min_t(size_t, PAGE_SIZE - offset, size), offset);
    size -= min_t(size_t, PAGE_SIZE - offset, size);
    for (i = 1; i < nr_pages; i++) {
        if (NULL == pages[i])
            goto nopage;
        if (PageHighMem(pages[i]))
            goto highmem;
        sg_set_page(&sglist[i], pages[i], min_t(size_t, PAGE_SIZE, size), 0);
        size -= min_t(size_t, PAGE_SIZE, size);
    }
    return sglist;

nopage:
    dprintk(2, "sgl: oops - no page\n");
    vfree(sglist);
    return NULL;

highmem:
    dprintk(2, "sgl: oops - highmem page\n");
    vfree(sglist);
    return NULL;
}

/* --------------------------------------------------------------------- */

struct videobuf_dmabuf *videobuf_to_dma(struct videobuf_buffer *buf)
{
    struct videobuf_dma_sg_memory *mem = buf->priv;
    BUG_ON(!mem);

    MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);

    return &mem->dma;
}
EXPORT_SYMBOL_GPL(videobuf_to_dma);

void videobuf_dma_init(struct videobuf_dmabuf *dma)
{
    memset(dma, 0, sizeof(*dma));
    dma->magic = MAGIC_DMABUF;
}
EXPORT_SYMBOL_GPL(videobuf_dma_init);

static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma,
            int direction, unsigned long data, unsigned long size)
{
    unsigned long first, last;
    int err, rw = 0;

    dma->direction = direction;
    switch (dma->direction) {
    case DMA_FROM_DEVICE:
        rw = READ;
        break;
    case DMA_TO_DEVICE:
        rw = WRITE;
        break;
    default:
        BUG();
    }

    first = (data          & PAGE_MASK) >> PAGE_SHIFT;
    last  = ((data+size-1) & PAGE_MASK) >> PAGE_SHIFT;
    dma->offset = data & ~PAGE_MASK;
    dma->size = size;
    dma->nr_pages = last-first+1;
    dma->pages = kmalloc(dma->nr_pages * sizeof(struct page *), GFP_KERNEL);
    if (NULL == dma->pages)
        return -ENOMEM;

    dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n",
        data, size, dma->nr_pages);

    err = get_user_pages(current, current->mm,
                 data & PAGE_MASK, dma->nr_pages,
                 rw == READ, 1, /* force */
                 dma->pages, NULL);

    if (err != dma->nr_pages) {
        dma->nr_pages = (err >= 0) ? err : 0;
        dprintk(1, "get_user_pages: err=%d [%d]\n", err, dma->nr_pages);
        return err < 0 ? err : -EINVAL;
    }
    return 0;
}

int videobuf_dma_init_user(struct videobuf_dmabuf *dma, int direction,
               unsigned long data, unsigned long size)
{
    int ret;

    down_read(&current->mm->mmap_sem);
    ret = videobuf_dma_init_user_locked(dma, direction, data, size);
    up_read(&current->mm->mmap_sem);

    return ret;
}
EXPORT_SYMBOL_GPL(videobuf_dma_init_user);

int videobuf_dma_init_kernel(struct videobuf_dmabuf *dma, int direction,
                 int nr_pages)
{
    dprintk(1, "init kernel [%d pages]\n", nr_pages);

    dma->direction = direction;
    dma->vaddr = vmalloc_32(nr_pages << PAGE_SHIFT);
    if (NULL == dma->vaddr) {
        dprintk(1, "vmalloc_32(%d pages) failed\n", nr_pages);
        return -ENOMEM;
    }

    dprintk(1, "vmalloc is at addr 0x%08lx, size=%d\n",
                (unsigned long)dma->vaddr,
                nr_pages << PAGE_SHIFT);

    memset(dma->vaddr, 0, nr_pages << PAGE_SHIFT);
    dma->nr_pages = nr_pages;

    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_dma_init_kernel);

int videobuf_dma_init_overlay(struct videobuf_dmabuf *dma, int direction,
                  dma_addr_t addr, int nr_pages)
{
    dprintk(1, "init overlay [%d pages @ bus 0x%lx]\n",
        nr_pages, (unsigned long)addr);
    dma->direction = direction;

    if (0 == addr)
        return -EINVAL;

    dma->bus_addr = addr;
    dma->nr_pages = nr_pages;

    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_dma_init_overlay);

int videobuf_dma_map(struct device *dev, struct videobuf_dmabuf *dma)
{
    MAGIC_CHECK(dma->magic, MAGIC_DMABUF);
    BUG_ON(0 == dma->nr_pages);

    if (dma->pages) {
        dma->sglist = videobuf_pages_to_sg(dma->pages, dma->nr_pages,
                           dma->offset, dma->size);
    }
    if (dma->vaddr) {
        dma->sglist = videobuf_vmalloc_to_sg(dma->vaddr,
                             dma->nr_pages);
    }
    if (dma->bus_addr) {
        dma->sglist = vmalloc(sizeof(*dma->sglist));
        if (NULL != dma->sglist) {
            dma->sglen = 1;
            sg_dma_address(&dma->sglist[0]) = dma->bus_addr
                            & PAGE_MASK;
            dma->sglist[0].offset = dma->bus_addr & ~PAGE_MASK;
            sg_dma_len(&dma->sglist[0]) = dma->nr_pages * PAGE_SIZE;
        }
    }
    if (NULL == dma->sglist) {
        dprintk(1, "scatterlist is NULL\n");
        return -ENOMEM;
    }
    if (!dma->bus_addr) {
        dma->sglen = dma_map_sg(dev, dma->sglist,
                    dma->nr_pages, dma->direction);
        if (0 == dma->sglen) {
            printk(KERN_WARNING
                   "%s: videobuf_map_sg failed\n", __func__);
            vfree(dma->sglist);
            dma->sglist = NULL;
            dma->sglen = 0;
            return -ENOMEM;
        }
    }

    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_dma_map);

int videobuf_dma_unmap(struct device *dev, struct videobuf_dmabuf *dma)
{
    MAGIC_CHECK(dma->magic, MAGIC_DMABUF);

    if (!dma->sglen)
        return 0;

    dma_unmap_sg(dev, dma->sglist, dma->sglen, dma->direction);

    vfree(dma->sglist);
    dma->sglist = NULL;
    dma->sglen = 0;

    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_dma_unmap);

int videobuf_dma_free(struct videobuf_dmabuf *dma)
{
    int i;
    MAGIC_CHECK(dma->magic, MAGIC_DMABUF);
    BUG_ON(dma->sglen);

    if (dma->pages) {
        for (i = 0; i < dma->nr_pages; i++)
            page_cache_release(dma->pages[i]);
        kfree(dma->pages);
        dma->pages = NULL;
    }

    vfree(dma->vaddr);
    dma->vaddr = NULL;

    if (dma->bus_addr)
        dma->bus_addr = 0;
    dma->direction = DMA_NONE;

    return 0;
}
EXPORT_SYMBOL_GPL(videobuf_dma_free);

/* --------------------------------------------------------------------- */

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

    dprintk(2, "vm_open %p [count=%d,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;
    struct videobuf_dma_sg_memory *mem;
    int i;

    dprintk(2, "vm_close %p [count=%d,vma=%08lx-%08lx]\n", map,
        map->count, vma->vm_start, vma->vm_end);

    map->count--;
    if (0 == map->count) {
        dprintk(1, "munmap %p q=%p\n", map, q);
        videobuf_queue_lock(q);
        for (i = 0; i < VIDEO_MAX_FRAME; i++) {
            if (NULL == q->bufs[i])
                continue;
            mem = q->bufs[i]->priv;
            if (!mem)
                continue;

            MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);

            if (q->bufs[i]->map != map)
                continue;
            q->bufs[i]->map   = NULL;
            q->bufs[i]->baddr = 0;
            q->ops->buf_release(q, q->bufs[i]);
        }
        videobuf_queue_unlock(q);
        kfree(map);
    }
    return;
}

/*
 * Get a anonymous page for the mapping.  Make sure we can DMA to that
 * memory location with 32bit PCI devices (i.e. don't use highmem for
 * now ...).  Bounce buffers don't work very well for the data rates
 * video capture has.
 */
static int videobuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
    struct page *page;

    dprintk(3, "fault: fault @ %08lx [vma %08lx-%08lx]\n",
        (unsigned long)vmf->virtual_address,
        vma->vm_start, vma->vm_end);

    page = alloc_page(GFP_USER | __GFP_DMA32);
    if (!page)
        return VM_FAULT_OOM;
    clear_user_highpage(page, (unsigned long)vmf->virtual_address);
    vmf->page = page;

    return 0;
}

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

/* ---------------------------------------------------------------------
 * SG handlers for the generic methods
 */

/* Allocated area consists on 3 parts:
    struct video_buffer
    struct <driver>_buffer (cx88_buffer, saa7134_buf, ...)
    struct videobuf_dma_sg_memory
 */

static struct videobuf_buffer *__videobuf_alloc_vb(size_t size)
{
    struct videobuf_dma_sg_memory *mem;
    struct videobuf_buffer *vb;

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

    mem = vb->priv = ((char *)vb) + size;
    mem->magic = MAGIC_SG_MEM;

    videobuf_dma_init(&mem->dma);

    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 void *__videobuf_to_vaddr(struct videobuf_buffer *buf)
{
    struct videobuf_dma_sg_memory *mem = buf->priv;
    BUG_ON(!mem);

    MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);

    return mem->dma.vaddr;
}

static int __videobuf_iolock(struct videobuf_queue *q,
                 struct videobuf_buffer *vb,
                 struct v4l2_framebuffer *fbuf)
{
    int err, pages;
    dma_addr_t bus;
    struct videobuf_dma_sg_memory *mem = vb->priv;
    BUG_ON(!mem);

    MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);

    switch (vb->memory) {
    case V4L2_MEMORY_MMAP:
    case V4L2_MEMORY_USERPTR:
        if (0 == vb->baddr) {
            /* no userspace addr -- kernel bounce buffer */
            pages = PAGE_ALIGN(vb->size) >> PAGE_SHIFT;
            err = videobuf_dma_init_kernel(&mem->dma,
                               DMA_FROM_DEVICE,
                               pages);
            if (0 != err)
                return err;
        } else if (vb->memory == V4L2_MEMORY_USERPTR) {
            /* dma directly to userspace */
            err = videobuf_dma_init_user(&mem->dma,
                             DMA_FROM_DEVICE,
                             vb->baddr, vb->bsize);
            if (0 != err)
                return err;
        } else {
            /* NOTE: HACK: videobuf_iolock on V4L2_MEMORY_MMAP
            buffers can only be called from videobuf_qbuf
            we take current->mm->mmap_sem there, to prevent
            locking inversion, so don't take it here */

            err = videobuf_dma_init_user_locked(&mem->dma,
                              DMA_FROM_DEVICE,
                              vb->baddr, vb->bsize);
            if (0 != err)
                return err;
        }
        break;
    case V4L2_MEMORY_OVERLAY:
        if (NULL == fbuf)
            return -EINVAL;
        /* FIXME: need sanity checks for vb->boff */
        /*
         * Using a double cast to avoid compiler warnings when
         * building for PAE. Compiler doesn't like direct casting
         * of a 32 bit ptr to 64 bit integer.
         */
        bus   = (dma_addr_t)(unsigned long)fbuf->base + vb->boff;
        pages = PAGE_ALIGN(vb->size) >> PAGE_SHIFT;
        err = videobuf_dma_init_overlay(&mem->dma, DMA_FROM_DEVICE,
                        bus, pages);
        if (0 != err)
            return err;
        break;
    default:
        BUG();
    }
    err = videobuf_dma_map(q->dev, &mem->dma);
    if (0 != err)
        return err;

    return 0;
}

static int __videobuf_sync(struct videobuf_queue *q,
               struct videobuf_buffer *buf)
{
    struct videobuf_dma_sg_memory *mem = buf->priv;
    BUG_ON(!mem || !mem->dma.sglen);

    MAGIC_CHECK(mem->magic, MAGIC_SG_MEM);
    MAGIC_CHECK(mem->dma.magic, MAGIC_DMABUF);

    dma_sync_sg_for_cpu(q->dev, mem->dma.sglist,
                mem->dma.sglen, mem->dma.direction);

    return 0;
}

static int __videobuf_mmap_mapper(struct videobuf_queue *q,
                  struct videobuf_buffer *buf,
                  struct vm_area_struct *vma)
{
    struct videobuf_dma_sg_memory *mem = buf->priv;
    struct videobuf_mapping *map;
    unsigned int first, last, size = 0, i;
    int retval;

    retval = -EINVAL;

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

    /* look for first buffer to map */
    for (first = 0; first < VIDEO_MAX_FRAME; first++) {
        if (buf == q->bufs[first]) {
            size = PAGE_ALIGN(q->bufs[first]->bsize);
            break;
        }
    }

    /* paranoia, should never happen since buf is always valid. */
    if (!size) {
        dprintk(1, "mmap app bug: offset invalid [offset=0x%lx]\n",
                (vma->vm_pgoff << PAGE_SHIFT));
        goto done;
    }

    last = first;

    /* create mapping + update buffer list */
    retval = -ENOMEM;
    map = kmalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
    if (NULL == map)
        goto done;

    size = 0;
    for (i = first; i <= last; i++) {
        if (NULL == q->bufs[i])
            continue;
        q->bufs[i]->map   = map;
        q->bufs[i]->baddr = vma->vm_start + size;
        size += PAGE_ALIGN(q->bufs[i]->bsize);
    }

    map->count    = 1;
    map->q        = q;
    vma->vm_ops   = &videobuf_vm_ops;
    vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
    vma->vm_flags &= ~VM_IO; /* using shared anonymous pages */
    vma->vm_private_data = map;
    dprintk(1, "mmap %p: q=%p %08lx-%08lx pgoff %08lx bufs %d-%d\n",
        map, q, vma->vm_start, vma->vm_end, vma->vm_pgoff, first, last);
    retval = 0;

done:
    return retval;
}

static struct videobuf_qtype_ops sg_ops = {
    .magic        = MAGIC_QTYPE_OPS,

    .alloc_vb     = __videobuf_alloc_vb,
    .iolock       = __videobuf_iolock,
    .sync         = __videobuf_sync,
    .mmap_mapper  = __videobuf_mmap_mapper,
    .vaddr        = __videobuf_to_vaddr,
};

void *videobuf_sg_alloc(size_t size)
{
    struct videobuf_queue q;

    /* Required to make generic handler to call __videobuf_alloc */
    q.int_ops = &sg_ops;

    q.msize = size;

    return videobuf_alloc_vb(&q);
}
EXPORT_SYMBOL_GPL(videobuf_sg_alloc);

void videobuf_queue_sg_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, &sg_ops, ext_lock);
}
EXPORT_SYMBOL_GPL(videobuf_queue_sg_init);