tizen 2.3 releasetizen_2.3_releasesubmit/tizen_2.3/20150202.062707tizen_2.3

1 files changed, 651 insertions, 0 deletions

diff --git a/sys/v4l2/gstv4l2bufferpool.c b/sys/v4l2/gstv4l2bufferpool.c
new file mode 100644
index 0000000..51cc0ce
--- /dev/null
+++ b/sys/v4l2/gstv4l2bufferpool.c
@@ -0,0 +1,651 @@
+/* GStreamer
+ *
+ * Copyright (C) 2001-2002 Ronald Bultje <rbultje@ronald.bitfreak.net>
+ *               2006 Edgard Lima <edgard.lima@indt.org.br>
+ *               2009 Texas Instruments, Inc - http://www.ti.com/
+ *
+ * gstv4l2bufferpool.c V4L2 buffer pool class
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <sys/mman.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "gst/video/video.h"
+
+#include <gstv4l2bufferpool.h>
+#include "gstv4l2src.h"
+#ifdef HAVE_EXPERIMENTAL
+#include "gstv4l2sink.h"
+#endif
+#include "v4l2_calls.h"
+#include "gst/gst-i18n-plugin.h"
+#include <gst/glib-compat-private.h>
+
+/* videodev2.h is not versioned and we can't easily check for the presence
+ * of enum values at compile time, but the V4L2_CAP_VIDEO_OUTPUT_OVERLAY define
+ * was added in the same commit as V4L2_FIELD_INTERLACED_{TB,BT} (b2787845) */
+#ifndef V4L2_CAP_VIDEO_OUTPUT_OVERLAY
+#define V4L2_FIELD_INTERLACED_TB 8
+#define V4L2_FIELD_INTERLACED_BT 9
+#endif
+
+
+GST_DEBUG_CATEGORY_EXTERN (v4l2_debug);
+#define GST_CAT_DEFAULT v4l2_debug
+
+
+/*
+ * GstV4l2Buffer:
+ */
+
+static GstBufferClass *v4l2buffer_parent_class = NULL;
+
+static void
+gst_v4l2_buffer_finalize (GstV4l2Buffer * buffer)
+{
+  GstV4l2BufferPool *pool;
+  gboolean resuscitated = FALSE;
+  gint index;
+
+  pool = buffer->pool;
+
+  index = buffer->vbuffer.index;
+
+  GST_LOG_OBJECT (pool->v4l2elem, "finalizing buffer %p %d", buffer, index);
+
+  GST_V4L2_BUFFER_POOL_LOCK (pool);
+  if (pool->running) {
+    if (pool->requeuebuf) {
+      if (!gst_v4l2_buffer_pool_qbuf (pool, buffer)) {
+        GST_WARNING ("could not requeue buffer %p %d", buffer, index);
+      } else {
+        resuscitated = TRUE;
+      }
+    } else {
+      resuscitated = TRUE;
+      /* XXX double check this... I think it is ok to not synchronize this
+       * w.r.t. destruction of the pool, since the buffer is still live and
+       * the buffer holds a ref to the pool..
+       */
+      g_async_queue_push (pool->avail_buffers, buffer);
+    }
+  } else {
+    GST_LOG_OBJECT (pool->v4l2elem, "the pool is shutting down");
+  }
+
+  if (resuscitated) {
+    /* FIXME: check that the caps didn't change */
+    GST_LOG_OBJECT (pool->v4l2elem, "reviving buffer %p, %d", buffer, index);
+    gst_buffer_ref (GST_BUFFER (buffer));
+    GST_BUFFER_SIZE (buffer) = 0;
+    pool->buffers[index] = buffer;
+  }
+
+  GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+
+  if (!resuscitated) {
+    GST_LOG_OBJECT (pool->v4l2elem,
+        "buffer %p (data %p, len %u) not recovered, unmapping",
+        buffer, GST_BUFFER_DATA (buffer), buffer->vbuffer.length);
+    gst_mini_object_unref (GST_MINI_OBJECT (pool));
+    v4l2_munmap ((void *) GST_BUFFER_DATA (buffer), buffer->vbuffer.length);
+
+    GST_MINI_OBJECT_CLASS (v4l2buffer_parent_class)->finalize (GST_MINI_OBJECT
+        (buffer));
+  }
+}
+
+static void
+gst_v4l2_buffer_class_init (gpointer g_class, gpointer class_data)
+{
+  GstMiniObjectClass *mini_object_class = GST_MINI_OBJECT_CLASS (g_class);
+
+  v4l2buffer_parent_class = g_type_class_peek_parent (g_class);
+
+  mini_object_class->finalize = (GstMiniObjectFinalizeFunction)
+      gst_v4l2_buffer_finalize;
+}
+
+GType
+gst_v4l2_buffer_get_type (void)
+{
+  static GType _gst_v4l2_buffer_type;
+
+  if (G_UNLIKELY (_gst_v4l2_buffer_type == 0)) {
+    static const GTypeInfo v4l2_buffer_info = {
+      sizeof (GstBufferClass),
+      NULL,
+      NULL,
+      gst_v4l2_buffer_class_init,
+      NULL,
+      NULL,
+      sizeof (GstV4l2Buffer),
+      0,
+      NULL,
+      NULL
+    };
+    _gst_v4l2_buffer_type = g_type_register_static (GST_TYPE_BUFFER,
+        "GstV4l2Buffer", &v4l2_buffer_info, 0);
+  }
+  return _gst_v4l2_buffer_type;
+}
+
+static GstV4l2Buffer *
+gst_v4l2_buffer_new (GstV4l2BufferPool * pool, guint index, GstCaps * caps)
+{
+  GstV4l2Buffer *ret;
+  guint8 *data;
+
+  ret = (GstV4l2Buffer *) gst_mini_object_new (GST_TYPE_V4L2_BUFFER);
+
+  GST_LOG_OBJECT (pool->v4l2elem, "creating buffer %u, %p in pool %p", index,
+      ret, pool);
+
+  ret->pool =
+      (GstV4l2BufferPool *) gst_mini_object_ref (GST_MINI_OBJECT (pool));
+
+  ret->vbuffer.index = index;
+  ret->vbuffer.type = pool->type;
+  ret->vbuffer.memory = V4L2_MEMORY_MMAP;
+
+  if (v4l2_ioctl (pool->video_fd, VIDIOC_QUERYBUF, &ret->vbuffer) < 0)
+    goto querybuf_failed;
+
+  GST_LOG_OBJECT (pool->v4l2elem, "  index:     %u", ret->vbuffer.index);
+  GST_LOG_OBJECT (pool->v4l2elem, "  type:      %d", ret->vbuffer.type);
+  GST_LOG_OBJECT (pool->v4l2elem, "  bytesused: %u", ret->vbuffer.bytesused);
+  GST_LOG_OBJECT (pool->v4l2elem, "  flags:     %08x", ret->vbuffer.flags);
+  GST_LOG_OBJECT (pool->v4l2elem, "  field:     %d", ret->vbuffer.field);
+  GST_LOG_OBJECT (pool->v4l2elem, "  memory:    %d", ret->vbuffer.memory);
+  if (ret->vbuffer.memory == V4L2_MEMORY_MMAP)
+    GST_LOG_OBJECT (pool->v4l2elem, "  MMAP offset:  %u",
+        ret->vbuffer.m.offset);
+  GST_LOG_OBJECT (pool->v4l2elem, "  length:    %u", ret->vbuffer.length);
+
+  data = (guint8 *) v4l2_mmap (0, ret->vbuffer.length,
+      PROT_READ | PROT_WRITE, MAP_SHARED, pool->video_fd,
+      ret->vbuffer.m.offset);
+
+  if (data == MAP_FAILED)
+    goto mmap_failed;
+
+  GST_BUFFER_DATA (ret) = data;
+  GST_BUFFER_SIZE (ret) = ret->vbuffer.length;
+
+  GST_BUFFER_FLAG_SET (ret, GST_BUFFER_FLAG_READONLY);
+
+  gst_buffer_set_caps (GST_BUFFER (ret), caps);
+
+  return ret;
+
+  /* ERRORS */
+querybuf_failed:
+  {
+    gint errnosave = errno;
+
+    GST_WARNING ("Failed QUERYBUF: %s", g_strerror (errnosave));
+    gst_buffer_unref (GST_BUFFER (ret));
+    errno = errnosave;
+    return NULL;
+  }
+mmap_failed:
+  {
+    gint errnosave = errno;
+
+    GST_WARNING ("Failed to mmap: %s", g_strerror (errnosave));
+    gst_buffer_unref (GST_BUFFER (ret));
+    errno = errnosave;
+    return NULL;
+  }
+}
+
+
+/*
+ * GstV4l2BufferPool:
+ */
+
+static GstMiniObjectClass *buffer_pool_parent_class = NULL;
+
+static void
+gst_v4l2_buffer_pool_finalize (GstV4l2BufferPool * pool)
+{
+  g_mutex_free (pool->lock);
+  pool->lock = NULL;
+
+  g_async_queue_unref (pool->avail_buffers);
+  pool->avail_buffers = NULL;
+
+  if (pool->video_fd >= 0)
+    v4l2_close (pool->video_fd);
+
+  if (pool->buffers) {
+    g_free (pool->buffers);
+    pool->buffers = NULL;
+  }
+
+  GST_MINI_OBJECT_CLASS (buffer_pool_parent_class)->finalize (GST_MINI_OBJECT
+      (pool));
+}
+
+static void
+gst_v4l2_buffer_pool_init (GstV4l2BufferPool * pool, gpointer g_class)
+{
+  pool->lock = g_mutex_new ();
+  pool->running = FALSE;
+  pool->num_live_buffers = 0;
+}
+
+static void
+gst_v4l2_buffer_pool_class_init (gpointer g_class, gpointer class_data)
+{
+  GstMiniObjectClass *mini_object_class = GST_MINI_OBJECT_CLASS (g_class);
+
+  buffer_pool_parent_class = g_type_class_peek_parent (g_class);
+
+  mini_object_class->finalize = (GstMiniObjectFinalizeFunction)
+      gst_v4l2_buffer_pool_finalize;
+}
+
+GType
+gst_v4l2_buffer_pool_get_type (void)
+{
+  static GType _gst_v4l2_buffer_pool_type;
+
+  if (G_UNLIKELY (_gst_v4l2_buffer_pool_type == 0)) {
+    static const GTypeInfo v4l2_buffer_pool_info = {
+      sizeof (GstMiniObjectClass),
+      NULL,
+      NULL,
+      gst_v4l2_buffer_pool_class_init,
+      NULL,
+      NULL,
+      sizeof (GstV4l2BufferPool),
+      0,
+      (GInstanceInitFunc) gst_v4l2_buffer_pool_init,
+      NULL
+    };
+    _gst_v4l2_buffer_pool_type = g_type_register_static (GST_TYPE_MINI_OBJECT,
+        "GstV4l2BufferPool", &v4l2_buffer_pool_info, 0);
+  }
+  return _gst_v4l2_buffer_pool_type;
+}
+
+
+/* this is somewhat of a hack.. but better to keep the hack in
+ * one place than copy/pasting it around..
+ */
+static GstV4l2Object *
+get_v4l2_object (GstElement * v4l2elem)
+{
+  GstV4l2Object *v4l2object = NULL;
+  if (GST_IS_V4L2SRC (v4l2elem)) {
+    v4l2object = (GST_V4L2SRC (v4l2elem))->v4l2object;
+#ifdef HAVE_EXPERIMENTAL
+  } else if (GST_IS_V4L2SINK (v4l2elem)) {
+    v4l2object = (GST_V4L2SINK (v4l2elem))->v4l2object;
+#endif
+  } else {
+    GST_ERROR_OBJECT (v4l2elem, "unknown v4l2 element");
+  }
+  return v4l2object;
+}
+
+
+
+/**
+ * gst_v4l2_buffer_pool_new:
+ * @v4l2elem:  the v4l2 element (src or sink) that owns this pool
+ * @fd:   the video device file descriptor
+ * @num_buffers:  the requested number of buffers in the pool
+ * @caps:  the caps to set on the buffer
+ * @requeuebuf: if %TRUE, and if the pool is still in the running state, a
+ *  buffer with no remaining references is immediately passed back to v4l2
+ *  (VIDIOC_QBUF), otherwise it is returned to the pool of available buffers
+ *  (which can be accessed via gst_v4l2_buffer_pool_get().
+ *
+ * Construct a new buffer pool.
+ *
+ * Returns: the new pool, use gst_v4l2_buffer_pool_destroy() to free resources
+ */
+GstV4l2BufferPool *
+gst_v4l2_buffer_pool_new (GstElement * v4l2elem, gint fd, gint num_buffers,
+    GstCaps * caps, gboolean requeuebuf, enum v4l2_buf_type type)
+{
+  GstV4l2BufferPool *pool;
+  gint n;
+  struct v4l2_requestbuffers breq;
+
+  pool = (GstV4l2BufferPool *) gst_mini_object_new (GST_TYPE_V4L2_BUFFER_POOL);
+
+  pool->video_fd = v4l2_dup (fd);
+  if (pool->video_fd < 0)
+    goto dup_failed;
+
+
+  /* first, lets request buffers, and see how many we can get: */
+  GST_DEBUG_OBJECT (v4l2elem, "STREAMING, requesting %d MMAP buffers",
+      num_buffers);
+
+  memset (&breq, 0, sizeof (struct v4l2_requestbuffers));
+  breq.type = type;
+  breq.count = num_buffers;
+  breq.memory = V4L2_MEMORY_MMAP;
+
+  if (v4l2_ioctl (fd, VIDIOC_REQBUFS, &breq) < 0)
+    goto reqbufs_failed;
+
+  GST_LOG_OBJECT (v4l2elem, " count:  %u", breq.count);
+  GST_LOG_OBJECT (v4l2elem, " type:   %d", breq.type);
+  GST_LOG_OBJECT (v4l2elem, " memory: %d", breq.memory);
+
+  if (breq.count < GST_V4L2_MIN_BUFFERS)
+    goto no_buffers;
+
+  if (num_buffers != breq.count) {
+    GST_WARNING_OBJECT (v4l2elem, "using %u buffers instead", breq.count);
+    num_buffers = breq.count;
+  }
+
+  pool->v4l2elem = v4l2elem;
+  pool->requeuebuf = requeuebuf;
+  pool->type = type;
+  pool->buffer_count = num_buffers;
+  pool->buffers = g_new0 (GstV4l2Buffer *, num_buffers);
+  pool->avail_buffers = g_async_queue_new ();
+
+  /* now, map the buffers: */
+  for (n = 0; n < num_buffers; n++) {
+    pool->buffers[n] = gst_v4l2_buffer_new (pool, n, caps);
+    if (!pool->buffers[n])
+      goto buffer_new_failed;
+    pool->num_live_buffers++;
+    g_async_queue_push (pool->avail_buffers, pool->buffers[n]);
+  }
+
+  return pool;
+
+  /* ERRORS */
+dup_failed:
+  {
+    gint errnosave = errno;
+
+    gst_mini_object_unref (GST_MINI_OBJECT (pool));
+
+    errno = errnosave;
+
+    return NULL;
+  }
+reqbufs_failed:
+  {
+    GstV4l2Object *v4l2object = get_v4l2_object (v4l2elem);
+    GST_ELEMENT_ERROR (v4l2elem, RESOURCE, READ,
+        (_("Could not get buffers from device '%s'."),
+            v4l2object->videodev),
+        ("error requesting %d buffers: %s", num_buffers, g_strerror (errno)));
+    return NULL;
+  }
+no_buffers:
+  {
+    GstV4l2Object *v4l2object = get_v4l2_object (v4l2elem);
+    GST_ELEMENT_ERROR (v4l2elem, RESOURCE, READ,
+        (_("Could not get enough buffers from device '%s'."),
+            v4l2object->videodev),
+        ("we received %d from device '%s', we want at least %d",
+            breq.count, v4l2object->videodev, GST_V4L2_MIN_BUFFERS));
+    return NULL;
+  }
+buffer_new_failed:
+  {
+    gint errnosave = errno;
+
+    gst_v4l2_buffer_pool_destroy (pool);
+
+    errno = errnosave;
+
+    return NULL;
+  }
+}
+
+/**
+ * gst_v4l2_buffer_pool_destroy:
+ * @pool: the pool
+ *
+ * Free all resources in the pool and the pool itself.
+ */
+void
+gst_v4l2_buffer_pool_destroy (GstV4l2BufferPool * pool)
+{
+  gint n;
+
+  GST_V4L2_BUFFER_POOL_LOCK (pool);
+  pool->running = FALSE;
+  GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+
+  GST_DEBUG_OBJECT (pool->v4l2elem, "destroy pool");
+
+  /* after this point, no more buffers will be queued or dequeued; no buffer
+   * from pool->buffers that is NULL will be set to a buffer, and no buffer that
+   * is not NULL will be pushed out. */
+
+  /* miniobjects have no dispose, so they can't break ref-cycles, as buffers ref
+   * the pool, we need to unref the buffer to properly finalize te pool */
+  for (n = 0; n < pool->buffer_count; n++) {
+    GstBuffer *buf;
+
+    GST_V4L2_BUFFER_POOL_LOCK (pool);
+    buf = GST_BUFFER (pool->buffers[n]);
+    GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+
+    if (buf)
+      /* we own the ref if the buffer is in pool->buffers; drop it. */
+      gst_buffer_unref (buf);
+  }
+
+  gst_mini_object_unref (GST_MINI_OBJECT (pool));
+}
+
+/**
+ * gst_v4l2_buffer_pool_get:
+ * @pool:   the "this" object
+ * @blocking:  should this call suspend until there is a buffer available
+ *    in the buffer pool?
+ *
+ * Get an available buffer in the pool
+ */
+GstV4l2Buffer *
+gst_v4l2_buffer_pool_get (GstV4l2BufferPool * pool, gboolean blocking)
+{
+  GstV4l2Buffer *buf;
+
+  if (blocking) {
+    buf = g_async_queue_pop (pool->avail_buffers);
+  } else {
+    buf = g_async_queue_try_pop (pool->avail_buffers);
+  }
+
+  if (buf) {
+    GST_V4L2_BUFFER_POOL_LOCK (pool);
+    GST_BUFFER_SIZE (buf) = buf->vbuffer.length;
+    GST_BUFFER_FLAG_UNSET (buf, 0xffffffff);
+    GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+  }
+
+  pool->running = TRUE;
+
+  return buf;
+}
+
+
+/**
+ * gst_v4l2_buffer_pool_qbuf:
+ * @pool: the pool
+ * @buf: the buffer to queue
+ *
+ * Queue a buffer to the driver
+ *
+ * Returns: %TRUE for success
+ */
+gboolean
+gst_v4l2_buffer_pool_qbuf (GstV4l2BufferPool * pool, GstV4l2Buffer * buf)
+{
+  GST_LOG_OBJECT (pool->v4l2elem, "enqueue pool buffer %d", buf->vbuffer.index);
+
+  if (v4l2_ioctl (pool->video_fd, VIDIOC_QBUF, &buf->vbuffer) < 0)
+    return FALSE;
+
+  pool->num_live_buffers--;
+  GST_DEBUG_OBJECT (pool->v4l2elem, "num_live_buffers--: %d",
+      pool->num_live_buffers);
+
+  return TRUE;
+}
+
+/**
+ * gst_v4l2_buffer_pool_dqbuf:
+ * @pool: the pool
+ *
+ * Dequeue a buffer from the driver.  Some generic error handling is done in
+ * this function, but any error handling specific to v4l2src (capture) or
+ * v4l2sink (output) can be done outside this function by checking 'errno'
+ *
+ * Returns: a buffer
+ */
+GstV4l2Buffer *
+gst_v4l2_buffer_pool_dqbuf (GstV4l2BufferPool * pool)
+{
+  GstV4l2Object *v4l2object = get_v4l2_object (pool->v4l2elem);
+  GstV4l2Buffer *pool_buffer;
+  struct v4l2_buffer buffer;
+
+  memset (&buffer, 0x00, sizeof (buffer));
+  buffer.type = pool->type;
+  buffer.memory = V4L2_MEMORY_MMAP;
+
+
+  if (v4l2_ioctl (pool->video_fd, VIDIOC_DQBUF, &buffer) >= 0) {
+
+    GST_V4L2_BUFFER_POOL_LOCK (pool);
+
+    /* get our GstBuffer with that index from the pool, if the buffer was
+     * outstanding we have a serious problem.
+     */
+    pool_buffer = pool->buffers[buffer.index];
+
+    if (pool_buffer == NULL) {
+      GST_ELEMENT_ERROR (pool->v4l2elem, RESOURCE, FAILED,
+          (_("Failed trying to get video frames from device '%s'."),
+              v4l2object->videodev),
+          (_("No free buffers found in the pool at index %d."), buffer.index));
+      GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+      return NULL;
+    }
+
+    GST_LOG_OBJECT (pool->v4l2elem,
+        "grabbed frame %d (ix=%d), flags %08x, pool-ct=%d, buffer=%p",
+        buffer.sequence, buffer.index, buffer.flags, pool->num_live_buffers,
+        pool_buffer);
+
+    pool->num_live_buffers++;
+    GST_DEBUG_OBJECT (pool->v4l2elem, "num_live_buffers++: %d",
+        pool->num_live_buffers);
+
+    /* set top/bottom field first if v4l2_buffer has the information */
+    if (buffer.field == V4L2_FIELD_INTERLACED_TB)
+      GST_BUFFER_FLAG_SET (pool_buffer, GST_VIDEO_BUFFER_TFF);
+    if (buffer.field == V4L2_FIELD_INTERLACED_BT)
+      GST_BUFFER_FLAG_UNSET (pool_buffer, GST_VIDEO_BUFFER_TFF);
+
+    /* this can change at every frame, esp. with jpeg */
+    GST_BUFFER_SIZE (pool_buffer) = buffer.bytesused;
+
+    GST_V4L2_BUFFER_POOL_UNLOCK (pool);
+
+    return pool_buffer;
+  }
+
+
+  GST_WARNING_OBJECT (pool->v4l2elem,
+      "problem grabbing frame %d (ix=%d), pool-ct=%d, buf.flags=%d",
+      buffer.sequence, buffer.index,
+      GST_MINI_OBJECT_REFCOUNT (pool), buffer.flags);
+
+  switch (errno) {
+    case EAGAIN:
+      GST_WARNING_OBJECT (pool->v4l2elem,
+          "Non-blocking I/O has been selected using O_NONBLOCK and"
+          " no buffer was in the outgoing queue. device %s",
+          v4l2object->videodev);
+      break;
+    case EINVAL:
+      GST_ELEMENT_ERROR (pool->v4l2elem, RESOURCE, FAILED,
+          (_("Failed trying to get video frames from device '%s'."),
+              v4l2object->videodev),
+          (_("The buffer type is not supported, or the index is out of bounds,"
+                  " or no buffers have been allocated yet, or the userptr"
+                  " or length are invalid. device %s"), v4l2object->videodev));
+      break;
+    case ENOMEM:
+      GST_ELEMENT_ERROR (pool->v4l2elem, RESOURCE, FAILED,
+          (_("Failed trying to get video frames from device '%s'. Not enough memory."), v4l2object->videodev), (_("insufficient memory to enqueue a user pointer buffer. device %s."), v4l2object->videodev));
+      break;
+    case EIO:
+      GST_INFO_OBJECT (pool->v4l2elem,
+          "VIDIOC_DQBUF failed due to an internal error."
+          " Can also indicate temporary problems like signal loss."
+          " Note the driver might dequeue an (empty) buffer despite"
+          " returning an error, or even stop capturing."
+          " device %s", v4l2object->videodev);
+      /* have we de-queued a buffer ? */
+      if (!(buffer.flags & (V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE))) {
+        GST_DEBUG_OBJECT (pool->v4l2elem, "reenqueing buffer");
+        /* FIXME ... should we do something here? */
+      }
+      break;
+    case EINTR:
+      GST_WARNING_OBJECT (pool->v4l2elem,
+          "could not sync on a buffer on device %s", v4l2object->videodev);
+      break;
+    default:
+      GST_WARNING_OBJECT (pool->v4l2elem,
+          "Grabbing frame got interrupted on %s unexpectedly. %d: %s.",
+          v4l2object->videodev, errno, g_strerror (errno));
+      break;
+  }
+
+  return NULL;
+}
+
+/**
+ * gst_v4l2_buffer_pool_available_buffers:
+ * @pool: the pool
+ *
+ * Check the number of buffers available to the driver, ie. buffers that
+ * have been QBUF'd but not yet DQBUF'd.
+ *
+ * Returns: the number of buffers available.
+ */
+gint
+gst_v4l2_buffer_pool_available_buffers (GstV4l2BufferPool * pool)
+{
+  return pool->buffer_count - pool->num_live_buffers;
+}