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libv4l1.c

/*
# libv4l1 userspace v4l1 api emulation for v4l2 devices

#             (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl>

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* MAKING CHANGES TO THIS FILE??   READ THIS FIRST!!!

   Important note to people making changes to this file: All functions
   (v4l1_close, v4l1_ioctl, etc.) are designed to function as their regular
   counterpart when they get passed a fd that is not "registered" by libv4l1,
   there are 2 reasons for this:
   1) This allows us to get completely out of the way when dealing with non
      capture only devices, or non v4l2 devices.
   2) libv4l1 is the base of the v4l1compat.so wrapper lib, which is a .so
      which can be LD_PRELOAD-ed and the overrules the libc's open/close/etc,
      and when opening /dev/videoX or /dev/v4l/ calls v4l1_open. Because we
      behave as the regular counterpart when the fd is not known (instead of
      say throwing an error), v4l1compat.so can simply call the v4l1_ prefixed
      function for all wrapped functions. This way the wrapper does not have
      to keep track of which fd's are being handled by libv4l1, as libv4l1
      already keeps track of this itself.

      This also means that libv4l1 may not use any of the regular functions
      it mimics, as for example open could be a symbol in v4l1compat.so, which
      in turn will call v4l1_open, so therefor v4l1_open (for example) may not
      use the regular open()!
*/
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <syscall.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
/* These headers are not needed by us, but by linux/videodev2.h,
   which is broken on some systems and doesn't include them itself :( */
#include <sys/time.h>
#include <asm/types.h>
#include <linux/ioctl.h>
/* end broken header workaround includes */
#include <linux/videodev.h>
#include <linux/videodev2.h>
#include <libv4l2.h>
#include "libv4l1.h"
#include "libv4l1-priv.h"

#define V4L1_SUPPORTS_ENUMINPUT 0x01
#define V4L1_SUPPORTS_ENUMSTD   0x02
#define V4L1_PIX_FMT_TOUCHED    0x04
#define V4L1_PIX_SIZE_TOUCHED   0x08

static pthread_mutex_t v4l1_open_mutex = PTHREAD_MUTEX_INITIALIZER;
static struct v4l1_dev_info devices[V4L1_MAX_DEVICES] = { { .fd = -1 },
  { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 },
  { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 },
  { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 }, { .fd = -1 }};
static int devices_used = 0;

static unsigned int palette_to_pixelformat(unsigned int palette)
{
  switch (palette) {
    case VIDEO_PALETTE_GREY:
      return V4L2_PIX_FMT_GREY;
    case VIDEO_PALETTE_RGB555:
      return V4L2_PIX_FMT_RGB555;
    case VIDEO_PALETTE_RGB565:
      return V4L2_PIX_FMT_RGB565;
    case VIDEO_PALETTE_RGB24:
      return V4L2_PIX_FMT_BGR24;
    case VIDEO_PALETTE_RGB32:
      return V4L2_PIX_FMT_BGR32;
    case VIDEO_PALETTE_YUYV:
      return V4L2_PIX_FMT_YUYV;
    case VIDEO_PALETTE_YUV422:
      return V4L2_PIX_FMT_YUYV;
    case VIDEO_PALETTE_UYVY:
      return V4L2_PIX_FMT_UYVY;
    case VIDEO_PALETTE_YUV410P:
      return V4L2_PIX_FMT_YUV410;
    case VIDEO_PALETTE_YUV420:
    case VIDEO_PALETTE_YUV420P:
      return V4L2_PIX_FMT_YUV420;
    case VIDEO_PALETTE_YUV411P:
      return V4L2_PIX_FMT_YUV411P;
    case VIDEO_PALETTE_YUV422P:
      return V4L2_PIX_FMT_YUV422P;
  }
  return 0;
}

static unsigned int pixelformat_to_palette(unsigned int pixelformat)
{
  switch (pixelformat) {
    case V4L2_PIX_FMT_GREY:
      return VIDEO_PALETTE_GREY;
    case V4L2_PIX_FMT_RGB555:
      return VIDEO_PALETTE_RGB555;
    case V4L2_PIX_FMT_RGB565:
      return VIDEO_PALETTE_RGB565;
    case V4L2_PIX_FMT_BGR24:
      return VIDEO_PALETTE_RGB24;
    case V4L2_PIX_FMT_BGR32:
      return VIDEO_PALETTE_RGB32;
    case V4L2_PIX_FMT_YUYV:
      return VIDEO_PALETTE_YUYV;
    case V4L2_PIX_FMT_UYVY:
      return VIDEO_PALETTE_UYVY;
    case V4L2_PIX_FMT_YUV410:
    case V4L2_PIX_FMT_YUV420:
      return VIDEO_PALETTE_YUV420P;
    case V4L2_PIX_FMT_YUV411P:
      return VIDEO_PALETTE_YUV411P;
    case V4L2_PIX_FMT_YUV422P:
      return VIDEO_PALETTE_YUV422P;
  }
  return 0;
}

static int v4l1_set_format(int index, unsigned int width,
  unsigned int height, int v4l1_pal, int width_height_may_differ)
{
  int result;
  unsigned int v4l2_pixfmt;
  struct v4l2_format fmt2 = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };

  if (v4l1_pal != -1) {
    v4l2_pixfmt = palette_to_pixelformat(v4l1_pal);
    if (!v4l2_pixfmt) {
      V4L1_LOG("Unknown v4l1 palette number: %d\n", v4l1_pal);
      errno = EINVAL;
      return -1;
    }
  } else {
    v4l2_pixfmt = devices[index].v4l2_pixfmt;
    v4l1_pal = devices[index].v4l1_pal;
  }

  /* Do we need to change the resolution / format ? */
  if (width == devices[index].width && height == devices[index].height &&
      v4l2_pixfmt == devices[index].v4l2_pixfmt)
    return 0;

  /* Get current settings, apply our changes and try the new setting */
  if ((result = v4l2_ioctl(devices[index].fd, VIDIOC_G_FMT, &fmt2))) {
    int saved_err = errno;
    V4L1_LOG_ERR("getting pixformat: %s\n", strerror(errno));
    errno = saved_err;
    return result;
  }

  fmt2.fmt.pix.pixelformat = v4l2_pixfmt;
  fmt2.fmt.pix.width  = width;
  fmt2.fmt.pix.height = height;
  if ((result = v4l2_ioctl(devices[index].fd, VIDIOC_TRY_FMT, &fmt2)))
  {
    int saved_err = errno;
    V4L1_LOG("error trying pixformat: %s\n", strerror(errno));
    errno = saved_err;
    return result;
  }

  /* Check if we get what we asked for */
  if (fmt2.fmt.pix.pixelformat != v4l2_pixfmt || (!width_height_may_differ &&
       (fmt2.fmt.pix.width != width || fmt2.fmt.pix.height != height))) {
    V4L1_LOG("requested fmt, width, height combo not available\n");
    errno = EINVAL;
    return -1;
  }

  /* Maybe after the TRY_FMT things haven't changed after all ? */
  if (fmt2.fmt.pix.width  == devices[index].width &&
      fmt2.fmt.pix.height == devices[index].height &&
      fmt2.fmt.pix.pixelformat == devices[index].v4l2_pixfmt) {
    devices[index].v4l1_pal = v4l1_pal;
    return 0;
  }

  if ((result = v4l2_ioctl(devices[index].fd, VIDIOC_S_FMT, &fmt2))) {
    int saved_err = errno;
    V4L1_LOG_ERR("setting pixformat: %s\n", strerror(errno));
    errno = saved_err;
    return result;
  }

  devices[index].width  = fmt2.fmt.pix.width;
  devices[index].height = fmt2.fmt.pix.height;
  devices[index].v4l2_pixfmt = v4l2_pixfmt;
  devices[index].v4l1_pal = v4l1_pal;
  devices[index].depth = ((fmt2.fmt.pix.bytesperline << 3) +
                    (fmt2.fmt.pix.width - 1)) / fmt2.fmt.pix.width;

  return result;
}

static void v4l1_find_min_and_max_size(int index, struct v4l2_format *fmt2)
{
  int i;
  struct v4l2_fmtdesc fmtdesc2 = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };

  devices[index].min_width = -1;
  devices[index].min_height = -1;
  devices[index].max_width = 0;
  devices[index].max_height = 0;

  for (i = 0; ; i++) {
    fmtdesc2.index = i;

    if (syscall(SYS_ioctl, devices[index].fd, VIDIOC_ENUM_FMT, &fmtdesc2))
      break;

    fmt2->fmt.pix.pixelformat = fmtdesc2.pixelformat;
    fmt2->fmt.pix.width = 48;
    fmt2->fmt.pix.height = 32;

    if (syscall(SYS_ioctl, devices[index].fd, VIDIOC_TRY_FMT, fmt2) == 0) {
      if (fmt2->fmt.pix.width < devices[index].min_width)
      devices[index].min_width = fmt2->fmt.pix.width;
      if (fmt2->fmt.pix.height < devices[index].min_height)
      devices[index].min_height = fmt2->fmt.pix.height;
    }

    fmt2->fmt.pix.pixelformat = fmtdesc2.pixelformat;
    fmt2->fmt.pix.width = 100000;
    fmt2->fmt.pix.height = 100000;

    if (syscall(SYS_ioctl, devices[index].fd, VIDIOC_TRY_FMT, fmt2) == 0) {
      if (fmt2->fmt.pix.width > devices[index].max_width)
      devices[index].max_width = fmt2->fmt.pix.width;
      if (fmt2->fmt.pix.height > devices[index].max_height)
      devices[index].max_height = fmt2->fmt.pix.height;
    }
  }
}


int v4l1_open (const char *file, int oflag, ...)
{
  int index, fd;
  char *lfname;
  struct v4l2_capability cap2;
  struct v4l2_format fmt2;
  struct v4l2_input input2;
  struct v4l2_standard standard2;
  int v4l_device = 0;

  /* check if we're opening a video4linux2 device */
  if (!strncmp(file, "/dev/video", 10) || !strncmp(file, "/dev/v4l/", 9)) {
    /* Some apps open the device read only, but we need rw rights as the
       buffers *MUST* be mapped rw */
    oflag = (oflag & ~O_ACCMODE) | O_RDWR;
    v4l_device = 1;
  }

  /* original open code */
  if (oflag & O_CREAT)
  {
    va_list ap;
    mode_t mode;

    va_start (ap, oflag);
    mode = va_arg (ap, mode_t);

    fd = syscall(SYS_open, file, oflag, mode);

    va_end(ap);
  } else
    fd = syscall(SYS_open, file, oflag);
  /* end of original open code */

  if (fd == -1 || !v4l_device)
    return fd;

  /* check that this is an v4l2 device, no need to emulate v4l1 on
     a v4l1 device */
  if (syscall(SYS_ioctl, fd, VIDIOC_QUERYCAP, &cap2))
    return fd;

  /* IMPROVEME */
  /* we only support simple video capture devices which do not do overlay */
  if ((cap2.capabilities & 0x0F) != V4L2_CAP_VIDEO_CAPTURE)
    return fd;

  /* If no log file was set by the app, see if one was specified through the
     environment */
  if (!v4l1_log_file && (lfname = getenv("LIBV4L1_LOG_FILENAME")))
    v4l1_log_file = fopen(lfname, "w");

  /* redirect libv4l2 log messages to our logfile if no libv4l2 logfile is
     specified */
  if (!v4l2_log_file)
    v4l2_log_file = v4l1_log_file;

  /* Get initial width, height and pixelformat */
  fmt2.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  if (syscall(SYS_ioctl, fd, VIDIOC_G_FMT, &fmt2)) {
    int saved_err = errno;
    V4L1_LOG_ERR("getting pixformat: %s\n", strerror(errno));
    syscall(SYS_close, fd);
    errno = saved_err;
    return -1;
  }

  /* Register with libv4l2, as we use that todo format conversion and read()
     emulation for us */
  if (v4l2_fd_open(fd, V4L2_ENABLE_ENUM_FMT_EMULATION) == -1) {
    int saved_err = errno;
    syscall(SYS_close, fd);
    errno = saved_err;
    return -1;
  }

  /* So we have a device on which we can (and want to) emulate v4l1, register
     it in our devices array */
  pthread_mutex_lock(&v4l1_open_mutex);
  for (index = 0; index < V4L1_MAX_DEVICES; index++)
    if(devices[index].fd == -1) {
      devices[index].fd = fd;
      break;
    }
  pthread_mutex_unlock(&v4l1_open_mutex);

  if (index == V4L1_MAX_DEVICES) {
    V4L1_LOG_ERR("attempting to open more then %d video devices\n",
      V4L1_MAX_DEVICES);
    v4l2_close(fd);
    errno = EBUSY;
    return -1;
  }

  if (index >= devices_used)
    devices_used = index + 1;

  devices[index].flags = 0;
  devices[index].open_count = 1;
  devices[index].v4l1_frame_buf_map_count = 0;
  devices[index].v4l1_frame_pointer = MAP_FAILED;
  devices[index].width  = fmt2.fmt.pix.width;
  devices[index].height = fmt2.fmt.pix.height;
  devices[index].v4l2_pixfmt = fmt2.fmt.pix.pixelformat;
  devices[index].v4l1_pal = pixelformat_to_palette(fmt2.fmt.pix.pixelformat);
  devices[index].depth = ((fmt2.fmt.pix.bytesperline << 3) +
                    (fmt2.fmt.pix.width - 1)) / fmt2.fmt.pix.width;

  v4l1_find_min_and_max_size(index, &fmt2);

  /* Check ENUM_INPUT and ENUM_STD support */
  input2.index = 0;
  if (v4l2_ioctl(fd, VIDIOC_ENUMINPUT, &input2) == 0)
    devices[index].flags |= V4L1_SUPPORTS_ENUMINPUT;

  standard2.index = 0;
  if (v4l2_ioctl(fd, VIDIOC_ENUMSTD, &input2) == 0)
    devices[index].flags |= V4L1_SUPPORTS_ENUMSTD;

  V4L1_LOG("open: %d\n", fd);

  return fd;
}

/* Is this an fd for which we are emulating v4l1 ? */
static int v4l1_get_index(int fd)
{
  int index;

  /* We never handle fd -1 */
  if (fd == -1)
    return -1;

  for (index = 0; index < devices_used; index++)
    if (devices[index].fd == fd)
      break;

  if (index == devices_used)
    return -1;

  return index;
}


int v4l1_close(int fd) {
  int index, result;

  if ((index = v4l1_get_index(fd)) == -1)
    return syscall(SYS_close, fd);

  /* Abuse stream_lock to stop 2 closes from racing and trying to free the
     resources twice */
  pthread_mutex_lock(&devices[index].stream_lock);
  devices[index].open_count--;
  result = devices[index].open_count != 0;
  pthread_mutex_unlock(&devices[index].stream_lock);

  if (result)
    return v4l2_close(fd);

  /* Free resources */
  if (devices[index].v4l1_frame_pointer != MAP_FAILED) {
    if (devices[index].v4l1_frame_buf_map_count)
      V4L1_LOG("v4l1 capture buffer still mapped: %d times on close()\n",
      devices[index].v4l1_frame_buf_map_count);
    else
      syscall(SYS_munmap, devices[index].v4l1_frame_pointer,
            V4L1_NO_FRAMES * V4L1_FRAME_BUF_SIZE);
    devices[index].v4l1_frame_pointer = MAP_FAILED;
  }

  /* Remove the fd from our list of managed fds before closing it, because as
     soon as we've done the actual close the fd maybe returned by an open in
     another thread and we don't want to intercept calls to this new fd. */
  devices[index].fd = -1;

  result = v4l2_close(fd);

  V4L1_LOG("close: %d\n", fd);

  return result;
}

int v4l1_dup(int fd)
{
  int index;

  if ((index = v4l1_get_index(fd)) == -1)
    return syscall(SYS_dup, fd);

  devices[index].open_count++;

  return v4l2_dup(fd);
}


int v4l1_ioctl (int fd, unsigned long int request, ...)
{
  void *arg;
  va_list ap;
  int result, index, saved_err, stream_locked = 0;

  va_start (ap, request);
  arg = va_arg (ap, void *);
  va_end (ap);

  if ((index = v4l1_get_index(fd)) == -1)
    return syscall(SYS_ioctl, fd, request, arg);

  /* Appearantly the kernel and / or glibc ignore the 32 most significant bits
     when long = 64 bits, and some applications pass an int holding the req to
     ioctl, causing it to get sign extended, depending upon this behavior */
  request = (unsigned int)request;

  /* do we need to take the stream lock for this ioctl? */
  switch (request) {
    case VIDIOCSPICT:
    case VIDIOCGPICT:
    case VIDIOCSWIN:
    case VIDIOCGWIN:
    case VIDIOCGMBUF:
    case VIDIOCMCAPTURE:
    case VIDIOCSYNC:
    case VIDIOC_S_FMT:
      pthread_mutex_lock(&devices[index].stream_lock);
      stream_locked = 1;
  }

  switch (request) {

    case VIDIOCGCAP:
      {
      struct video_capability *cap = arg;

      result = syscall(SYS_ioctl, fd, request, arg);

      /* override kernel v4l1 compat min / max size with our own more
         accurate values */
      cap->minwidth  = devices[index].min_width;
      cap->minheight = devices[index].min_height;
      cap->maxwidth  = devices[index].max_width;
      cap->maxheight = devices[index].max_height;
      }
      break;

    case VIDIOCSPICT:
      {
      struct video_picture *pic = arg;

      devices[index].flags |= V4L1_PIX_FMT_TOUCHED;

      v4l2_set_control(fd, V4L2_CID_BRIGHTNESS, pic->brightness);
      v4l2_set_control(fd, V4L2_CID_HUE, pic->hue);
      v4l2_set_control(fd, V4L2_CID_CONTRAST, pic->contrast);
      v4l2_set_control(fd, V4L2_CID_SATURATION, pic->colour);
      v4l2_set_control(fd, V4L2_CID_WHITENESS, pic->whiteness);

      result = v4l1_set_format(index, devices[index].width,
               devices[index].height, pic->palette, 0);
      }
      break;

    case VIDIOCGPICT:
      {
      struct video_picture *pic = arg;

      /* If our v4l2 pixformat has no corresponding v4l1 palette, and the
         app has not touched the pixformat sofar, try setting a palette which
         does (and which we emulate when necessary) so that applications
         which just query the current format and then take whatever they get
         will work */
      if (!(devices[index].flags & V4L1_PIX_FMT_TOUCHED) &&
          !pixelformat_to_palette(devices[index].v4l2_pixfmt))
        v4l1_set_format(index, devices[index].width,
                         devices[index].height,
                         VIDEO_PALETTE_RGB24,
                         (devices[index].flags &
                          V4L1_PIX_SIZE_TOUCHED) ? 0 : 1);

      devices[index].flags |= V4L1_PIX_FMT_TOUCHED;

      pic->depth = devices[index].depth;
      pic->palette = devices[index].v4l1_pal;
      pic->hue = v4l2_get_control(devices[index].fd, V4L2_CID_HUE);
      pic->colour = v4l2_get_control(devices[index].fd, V4L2_CID_SATURATION);
      pic->contrast = v4l2_get_control(devices[index].fd, V4L2_CID_CONTRAST);
      pic->whiteness = v4l2_get_control(devices[index].fd,
                                 V4L2_CID_WHITENESS);
      pic->brightness = v4l2_get_control(devices[index].fd,
                                 V4L2_CID_BRIGHTNESS);

      result = 0;
      }
      break;

    case VIDIOCSWIN:
      {
      struct video_window *win = arg;

      devices[index].flags |= V4L1_PIX_SIZE_TOUCHED;

      result = v4l1_set_format(index, win->width, win->height, -1, 1);
      if (result == 0) {
        win->width  = devices[index].width;
        win->height = devices[index].height;
      }
      }
      break;

    case VIDIOCGWIN:
      devices[index].flags |= V4L1_PIX_SIZE_TOUCHED;
      result = syscall(SYS_ioctl, fd, request, arg);
      break;

    case VIDIOCGCHAN:
      {
      struct v4l2_input input2;
      struct video_channel *chan = arg;

      if ((devices[index].flags & V4L1_SUPPORTS_ENUMINPUT) &&
          (devices[index].flags & V4L1_SUPPORTS_ENUMSTD)) {
        result = syscall(SYS_ioctl, fd, request, arg);
        break;
      }

      /* Set some defaults */
      chan->tuners = 0;
      chan->flags = 0;
      chan->type = VIDEO_TYPE_CAMERA;
      chan->norm = 0;

      /* In case of no ENUMSTD support, ignore the norm member of the
         channel struct */
      if (devices[index].flags & V4L1_SUPPORTS_ENUMINPUT) {
        input2.index = chan->channel;
        result = v4l2_ioctl(fd, VIDIOC_ENUMINPUT, &input2);
        if (result == 0) {
          snprintf(chan->name, sizeof(chan->name), "%s", (char*)input2.name);
          if (input2.type == V4L2_INPUT_TYPE_TUNER) {
            chan->tuners = 1;
            chan->type = VIDEO_TYPE_TV;
            chan->flags = VIDEO_VC_TUNER;
          }
        }
        break;
      }

      /* No ENUMINPUT support, fake it (assume its a Camera in this case) */
      if (chan->channel == 0) {
        snprintf(chan->name, sizeof(chan->name), "Camera");
        result = 0;
      } else {
        errno  = EINVAL;
        result = -1;
      }
      }
      break;

    case VIDIOCSCHAN:
      {
      struct video_channel *chan = arg;
      if ((devices[index].flags & V4L1_SUPPORTS_ENUMINPUT) &&
          (devices[index].flags & V4L1_SUPPORTS_ENUMSTD)) {
        result = syscall(SYS_ioctl, fd, request, arg);
        break;
      }
      /* In case of no ENUMSTD support, ignore the norm member of the
         channel struct */
      if (devices[index].flags & V4L1_SUPPORTS_ENUMINPUT) {
        result = v4l2_ioctl(fd, VIDIOC_S_INPUT, &chan->channel);
        break;
      }
      /* No ENUMINPUT support, fake it (assume its a Camera in this case) */
      if (chan->channel == 0) {
        result = 0;
      } else {
        errno  = EINVAL;
        result = -1;
      }
      }
      break;

    case VIDIOCGMBUF:
      /* When VIDIOCGMBUF is done, we don't necessarrily know the format the
       application wants yet (with some apps this is passed for the first
       time through VIDIOCMCAPTURE), so we just create an anonymous mapping
       that should be large enough to hold any sort of frame. Note this only
       takes virtual memory, and does not use memory until actually used. */
      {
      int i;
      struct video_mbuf *mbuf = arg;

      mbuf->size = V4L1_NO_FRAMES * V4L1_FRAME_BUF_SIZE;
      mbuf->frames = V4L1_NO_FRAMES;
      for (i = 0; i < mbuf->frames; i++) {
        mbuf->offsets[i] = i * V4L1_FRAME_BUF_SIZE;
      }

      if (devices[index].v4l1_frame_pointer == MAP_FAILED) {
        devices[index].v4l1_frame_pointer = (void *)syscall(SYS_mmap2, NULL,
                              (size_t)mbuf->size,
                              PROT_READ|PROT_WRITE,
                              MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
        if (devices[index].v4l1_frame_pointer == MAP_FAILED) {
          saved_err = errno;
          V4L1_LOG_ERR("allocating v4l1 buffer: %s\n", strerror(errno));
          errno = saved_err;
          result = -1;
          break;
        }
        V4L1_LOG("allocated v4l1 buffer @ %p\n",
          devices[index].v4l1_frame_pointer);
      }
      result = 0;
      }
      break;

    case VIDIOCMCAPTURE:
      {
      struct video_mmap *map = arg;

      devices[index].flags |= V4L1_PIX_FMT_TOUCHED |
                        V4L1_PIX_SIZE_TOUCHED;

      result = v4l1_set_format(index, map->width, map->height,
                              map->format, 0);
      }
      break;

    case VIDIOCSYNC:
      {
      int *frame_index = arg;

      if (devices[index].v4l1_frame_pointer == MAP_FAILED ||
          *frame_index < 0 || *frame_index >= V4L1_NO_FRAMES) {
        errno = EINVAL;
        result = -1;
        break;
      }

      result = v4l2_read(devices[index].fd,
                  devices[index].v4l1_frame_pointer +
                  *frame_index * V4L1_FRAME_BUF_SIZE,
                  V4L1_FRAME_BUF_SIZE);
      result = (result > 0) ? 0:result;
      }
      break;

    /* We are passing through v4l2 calls to libv4l2 for applications which are
       using v4l2 through libv4l1 (possible with the v4l1compat.so wrapper).

       So the application could be calling VIDIOC_S_FMT, in this case update
       our own bookkeeping of the cam's format. Note that this really only is
       relevant if an application is mixing and matching v4l1 and v4l2 calls,
       which is crazy, but better safe then sorry. */
    case VIDIOC_S_FMT:
      {
      struct v4l2_format *fmt2 = arg;

      result = v4l2_ioctl(fd, request, arg);

      if (result == 0 && fmt2->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
        if (devices[index].v4l2_pixfmt != fmt2->fmt.pix.pixelformat) {
          devices[index].v4l2_pixfmt = fmt2->fmt.pix.pixelformat;
          devices[index].v4l1_pal =
            pixelformat_to_palette(fmt2->fmt.pix.pixelformat);
        }
        devices[index].width  = fmt2->fmt.pix.width;
        devices[index].height = fmt2->fmt.pix.height;
      }
      }
      break;

    default:
      /* Pass through libv4l2 for applications which are using v4l2 through
       libv4l1 (this can happen with the v4l1compat.so wrapper preloaded */
      result = v4l2_ioctl(fd, request, arg);
  }

  if (stream_locked)
    pthread_mutex_unlock(&devices[index].stream_lock);

  saved_err = errno;
  v4l1_log_ioctl(request, arg, result);
  errno = saved_err;

  return result;
}


ssize_t v4l1_read(int fd, void* buffer, size_t n)
{
  int index;
  ssize_t result;

  if ((index = v4l1_get_index(fd)) == -1)
    return syscall(SYS_read, fd, buffer, n);

  pthread_mutex_lock(&devices[index].stream_lock);
  result = v4l2_read(fd, buffer, n);
  pthread_mutex_unlock(&devices[index].stream_lock);

  return result;
}


void *v4l1_mmap(void *start, size_t length, int prot, int flags, int fd,
  __off64_t offset)
{
  int index;
  void *result;

  /* Check if the mmap data matches our answer to VIDIOCGMBUF, if not
     pass through libv4l2 for applications which are using v4l2 through
     libv4l1 (this can happen with the v4l1compat.so wrapper preloaded */
  if ((index = v4l1_get_index(fd)) == -1 || start || offset ||
      length != (V4L1_NO_FRAMES * V4L1_FRAME_BUF_SIZE))
    return v4l2_mmap(start, length, prot, flags, fd, offset);


  pthread_mutex_lock(&devices[index].stream_lock);

  /* It could be that we get called with an mmap which seems to match what
     we expect, but no VIDIOCGMBUF has been done yet, then it is certainly not
     for us so pass it through */
  if (devices[index].v4l1_frame_pointer == MAP_FAILED) {
    result = v4l2_mmap(start, length, prot, flags, fd, offset);
    goto leave;
  }

  devices[index].v4l1_frame_buf_map_count++;

  V4L1_LOG("v4l1 buffer @ %p mapped by application\n",
    devices[index].v4l1_frame_pointer);

  result = devices[index].v4l1_frame_pointer;

leave:
  pthread_mutex_unlock(&devices[index].stream_lock);

  return result;
}

int v4l1_munmap(void *_start, size_t length)
{
  int index;
  unsigned char *start = _start;

  /* Is this memory ours? */
  if (start != MAP_FAILED &&
      length == (V4L1_FRAME_BUF_SIZE * V4L1_NO_FRAMES)) {
    for (index = 0; index < devices_used; index++)
      if (devices[index].fd != -1 &&
        start == devices[index].v4l1_frame_pointer)
      break;

    if (index != devices_used) {
      int unmapped = 0;

      pthread_mutex_lock(&devices[index].stream_lock);

      /* Redo our checks now that we have the lock, things may have changed */
      if (start == devices[index].v4l1_frame_pointer) {
      if (devices[index].v4l1_frame_buf_map_count > 0)
        devices[index].v4l1_frame_buf_map_count--;

      unmapped = 1;
      }

      pthread_mutex_unlock(&devices[index].stream_lock);

      if (unmapped) {
      V4L1_LOG("v4l1 buffer munmap %p, %d\n", start, (int)length);
      return 0;
      }
    }
  }

  V4L1_LOG("v4l1 unknown munmap %p, %d\n", start, (int)length);

  /* If not pass through libv4l2 for applications which are using v4l2 through
     libv4l1 (this can happen with the v4l1compat.so wrapper preloaded */
  return v4l2_munmap(start, length);
}

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