gstreamer/sys/v4l2/v4l2_calls.c
Edgard Lima 8023d9492d Just make few things more robust and also some identation.
Original commit message from CVS:
Just make few things more robust and also some identation.
2006-03-25 05:31:28 +00:00

795 lines
23 KiB
C

/* G-Streamer generic V4L2 element - generic V4L2 calls handling
* Copyright (C) 2002 Ronald Bultje <rbultje@ronald.bitfreak.net>
*
* 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/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include "v4l2_calls.h"
#include "gstv4l2tuner.h"
#include "gstv4l2xoverlay.h"
#include "gstv4l2colorbalance.h"
#include "gstv4l2src.h"
GST_DEBUG_CATEGORY_EXTERN (v4l2_debug);
#define GST_CAT_DEFAULT v4l2_debug
/******************************************************
* gst_v4l2_get_capabilities():
* get the device's capturing capabilities
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_capabilities (GstV4l2Element * v4l2element)
{
GST_DEBUG ("getting capabilities");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_QUERYCAP, &(v4l2element->vcap)) < 0) {
GST_ERROR_OBJECT (v4l2element, "Error getting %s capabilities: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_empty_lists() and gst_v4l2_fill_lists():
* fill/empty the lists of enumerations
* return value: TRUE on success, FALSE on error
******************************************************/
static gboolean
gst_v4l2_fill_lists (GstV4l2Element * v4l2element)
{
gint n;
GstPadDirection dir = GST_PAD_UNKNOWN;
GST_DEBUG ("getting enumerations");
GST_V4L2_CHECK_OPEN (v4l2element);
if (dir != GST_PAD_SINK) {
/* and now, the inputs */
for (n = 0;; n++) {
struct v4l2_input input;
GstV4l2TunerChannel *v4l2channel;
GstTunerChannel *channel;
input.index = n;
if (ioctl (v4l2element->video_fd, VIDIOC_ENUMINPUT, &input) < 0) {
if (errno == EINVAL)
break; /* end of enumeration */
else {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get %d in input enumeration for %s: %s",
n, v4l2element->videodev, g_strerror (errno)));
return FALSE;
}
}
v4l2channel = g_object_new (GST_TYPE_V4L2_TUNER_CHANNEL, NULL);
channel = GST_TUNER_CHANNEL (v4l2channel);
channel->label = g_strdup ((const gchar *) input.name);
channel->flags = GST_TUNER_CHANNEL_INPUT;
v4l2channel->index = n;
if (input.type == V4L2_INPUT_TYPE_TUNER) {
struct v4l2_tuner vtun;
v4l2channel->tuner = input.tuner;
channel->flags |= GST_TUNER_CHANNEL_FREQUENCY;
vtun.index = input.tuner;
if (ioctl (v4l2element->video_fd, VIDIOC_G_TUNER, &vtun) < 0) {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get tuner %d settings on %s: %s",
input.tuner, v4l2element->videodev, g_strerror (errno)));
g_object_unref (G_OBJECT (channel));
return FALSE;
}
channel->freq_multiplicator =
62.5 * ((vtun.capability & V4L2_TUNER_CAP_LOW) ? 1 : 1000);
channel->min_frequency = vtun.rangelow * channel->freq_multiplicator;
channel->max_frequency = vtun.rangehigh * channel->freq_multiplicator;
channel->min_signal = 0;
channel->max_signal = 0xffff;
}
if (input.audioset) {
/* we take the first. We don't care for
* the others for now */
while (!(input.audioset & (1 << v4l2channel->audio)))
v4l2channel->audio++;
channel->flags |= GST_TUNER_CHANNEL_AUDIO;
}
v4l2element->inputs =
g_list_append (v4l2element->inputs, (gpointer) channel);
}
} else {
/* outputs */
for (n = 0;; n++) {
struct v4l2_output output;
GstV4l2TunerChannel *v4l2channel;
GstTunerChannel *channel;
output.index = n;
if (ioctl (v4l2element->video_fd, VIDIOC_ENUMOUTPUT, &output) < 0) {
if (errno == EINVAL)
break; /* end of enumeration */
else {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get %d in output enumeration for %s: %s",
n, v4l2element->videodev, g_strerror (errno)));
return FALSE;
}
}
v4l2channel = g_object_new (GST_TYPE_V4L2_TUNER_CHANNEL, NULL);
channel = GST_TUNER_CHANNEL (v4l2channel);
channel->label = g_strdup ((const gchar *) output.name);
channel->flags = GST_TUNER_CHANNEL_OUTPUT;
v4l2channel->index = n;
if (output.audioset) {
/* we take the first. We don't care for
* the others for now */
while (!(output.audioset & (1 << v4l2channel->audio)))
v4l2channel->audio++;
channel->flags |= GST_TUNER_CHANNEL_AUDIO;
}
v4l2element->inputs =
g_list_append (v4l2element->inputs, (gpointer) channel);
}
}
/* norms... */
for (n = 0;; n++) {
struct v4l2_standard standard;
GstV4l2TunerNorm *v4l2norm;
GstTunerNorm *norm;
standard.index = n;
if (ioctl (v4l2element->video_fd, VIDIOC_ENUMSTD, &standard) < 0) {
if (errno == EINVAL)
break; /* end of enumeration */
else {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get %d in norm enumeration for %s: %s",
n, v4l2element->videodev, g_strerror (errno)));
return FALSE;
}
}
v4l2norm = g_object_new (GST_TYPE_V4L2_TUNER_NORM, NULL);
norm = GST_TUNER_NORM (v4l2norm);
norm->label = g_strdup ((const gchar *) standard.name);
gst_value_set_fraction (&norm->framerate,
standard.frameperiod.denominator, standard.frameperiod.numerator);
v4l2norm->index = standard.id;
v4l2element->stds = g_list_append (v4l2element->stds, (gpointer) norm);
}
/* and lastly, controls+menus (if appropriate) */
for (n = V4L2_CID_BASE;; n++) {
struct v4l2_queryctrl control;
GstV4l2ColorBalanceChannel *v4l2channel;
GstColorBalanceChannel *channel;
/* hacky... */
if (n == V4L2_CID_LASTP1)
n = V4L2_CID_PRIVATE_BASE;
control.id = n;
if (ioctl (v4l2element->video_fd, VIDIOC_QUERYCTRL, &control) < 0) {
if (errno == EINVAL) {
if (n < V4L2_CID_PRIVATE_BASE)
continue;
else
break;
} else {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get %d in control enumeration for %s: %s",
n, v4l2element->videodev, g_strerror (errno)));
return FALSE;
}
}
if (control.flags & V4L2_CTRL_FLAG_DISABLED)
continue;
switch (n) {
case V4L2_CID_BRIGHTNESS:
case V4L2_CID_CONTRAST:
case V4L2_CID_SATURATION:
case V4L2_CID_HUE:
case V4L2_CID_BLACK_LEVEL:
case V4L2_CID_AUTO_WHITE_BALANCE:
case V4L2_CID_DO_WHITE_BALANCE:
case V4L2_CID_RED_BALANCE:
case V4L2_CID_BLUE_BALANCE:
case V4L2_CID_GAMMA:
case V4L2_CID_EXPOSURE:
case V4L2_CID_AUTOGAIN:
case V4L2_CID_GAIN:
/* we only handle these for now */
break;
default:
GST_DEBUG ("ControlID %s (%d) unhandled, FIXME", control.name, n);
control.id++;
break;
}
if (n != control.id)
continue;
v4l2channel = g_object_new (GST_TYPE_V4L2_COLOR_BALANCE_CHANNEL, NULL);
channel = GST_COLOR_BALANCE_CHANNEL (v4l2channel);
channel->label = g_strdup ((const gchar *) control.name);
v4l2channel->id = n;
#if 0
if (control.type == V4L2_CTRL_TYPE_MENU) {
struct v4l2_querymenu menu, *mptr;
int i;
menu.id = n;
for (i = 0;; i++) {
menu.index = i;
if (ioctl (v4l2element->video_fd, VIDIOC_QUERYMENU, &menu) < 0) {
if (errno == EINVAL)
break; /* end of enumeration */
else {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, SETTINGS, (NULL),
("Failed to get %d in menu enumeration for %s: %s",
n, v4l2element->videodev, g_strerror (errno)));
return FALSE;
}
}
mptr = g_malloc (sizeof (menu));
memcpy (mptr, &menu, sizeof (menu));
menus = g_list_append (menus, mptr);
}
}
v4l2element->menus = g_list_append (v4l2element->menus, menus);
#endif
switch (control.type) {
case V4L2_CTRL_TYPE_INTEGER:
channel->min_value = control.minimum;
channel->max_value = control.maximum;
break;
case V4L2_CTRL_TYPE_BOOLEAN:
channel->min_value = FALSE;
channel->max_value = TRUE;
break;
default:
channel->min_value = channel->max_value = 0;
break;
}
v4l2element->colors = g_list_append (v4l2element->colors,
(gpointer) channel);
}
return TRUE;
}
static void
gst_v4l2_empty_lists (GstV4l2Element * v4l2element)
{
GST_DEBUG ("deleting enumerations");
g_list_foreach (v4l2element->inputs, (GFunc) g_object_unref, NULL);
g_list_free (v4l2element->inputs);
v4l2element->inputs = NULL;
g_list_foreach (v4l2element->stds, (GFunc) g_object_unref, NULL);
g_list_free (v4l2element->stds);
v4l2element->stds = NULL;
g_list_foreach (v4l2element->colors, (GFunc) g_object_unref, NULL);
g_list_free (v4l2element->colors);
v4l2element->colors = NULL;
}
/* FIXME: move this stuff to gstv4l2tuner.c? */
static void
gst_v4l2_set_defaults (GstV4l2Element * v4l2element)
{
GstTunerNorm *norm = NULL;
GstTunerChannel *channel = NULL;
GstTuner *tuner = GST_TUNER (v4l2element);
if (v4l2element->std)
norm = gst_tuner_find_norm_by_name (tuner, v4l2element->std);
if (norm) {
gst_tuner_set_norm (tuner, norm);
} else {
norm = GST_TUNER_NORM (gst_tuner_get_norm (GST_TUNER (v4l2element)));
if (norm) {
v4l2element->std = g_strdup (norm->label);
gst_tuner_norm_changed (tuner, norm);
g_object_notify (G_OBJECT (v4l2element), "std");
}
}
if (v4l2element->input)
channel = gst_tuner_find_channel_by_name (tuner, v4l2element->input);
if (channel) {
gst_tuner_set_channel (tuner, channel);
} else {
channel =
GST_TUNER_CHANNEL (gst_tuner_get_channel (GST_TUNER (v4l2element)));
v4l2element->input = g_strdup (channel->label);
gst_tuner_channel_changed (tuner, channel);
g_object_notify (G_OBJECT (v4l2element), "input");
}
if (GST_TUNER_CHANNEL_HAS_FLAG (channel, GST_TUNER_CHANNEL_FREQUENCY)) {
if (v4l2element->frequency != 0) {
gst_tuner_set_frequency (tuner, channel, v4l2element->frequency);
} else {
v4l2element->frequency = gst_tuner_get_frequency (tuner, channel);
if (v4l2element->frequency == 0) {
/* guess */
gst_tuner_set_frequency (tuner, channel, 1000);
} else {
g_object_notify (G_OBJECT (v4l2element), "frequency");
}
}
}
}
/******************************************************
* gst_v4l2_open():
* open the video device (v4l2element->videodev)
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_open (GstV4l2Element * v4l2element)
{
struct stat st;
GST_DEBUG ("Trying to open device %s", v4l2element->videodev);
GST_V4L2_CHECK_NOT_OPEN (v4l2element);
GST_V4L2_CHECK_NOT_ACTIVE (v4l2element);
/* be sure we have a device */
if (!v4l2element->videodev)
v4l2element->videodev = g_strdup ("/dev/video");
/* check if it is a device */
if (-1 == stat (v4l2element->videodev, &st)) {
GST_ERROR ("Cannot identify '%s': %d, %s\n",
v4l2element->videodev, errno, strerror (errno));
goto error;
}
if (!S_ISCHR (st.st_mode)) {
GST_ERROR ("%s is no device\n", v4l2element->videodev);
goto error;
}
/* open the device */
v4l2element->video_fd = open (v4l2element->videodev,
O_RDWR /* | O_NONBLOCK */ );
if (!GST_V4L2_IS_OPEN (v4l2element)) {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, OPEN_READ_WRITE,
(_("Could not open device \"%s\" for reading and writing."),
v4l2element->videodev), GST_ERROR_SYSTEM);
goto error;
}
/* get capabilities */
if (!gst_v4l2_get_capabilities (v4l2element)) {
goto error;
}
/* do we need to be a capture device? */
if (GST_IS_V4L2SRC (v4l2element) &&
!(v4l2element->vcap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
GST_ELEMENT_ERROR (v4l2element, RESOURCE, NOT_FOUND,
(_("Device \"%s\" is not a capture device."),
v4l2element->videodev), ("Capabilities: 0x%x",
v4l2element->vcap.capabilities));
goto error;
}
/* create enumerations */
if (!gst_v4l2_fill_lists (v4l2element))
goto error;
/* set defaults */
gst_v4l2_set_defaults (v4l2element);
GST_INFO_OBJECT (v4l2element, "Opened device '%s' (%s) successfully\n",
v4l2element->vcap.card, v4l2element->videodev);
return TRUE;
error:
if (GST_V4L2_IS_OPEN (v4l2element)) {
/* close device */
close (v4l2element->video_fd);
v4l2element->video_fd = -1;
}
/* empty lists */
gst_v4l2_empty_lists (v4l2element);
return FALSE;
}
/******************************************************
* gst_v4l2_close():
* close the video device (v4l2element->video_fd)
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_close (GstV4l2Element * v4l2element)
{
GST_DEBUG ("Trying to close %s", v4l2element->videodev);
GST_V4L2_CHECK_OPEN (v4l2element);
GST_V4L2_CHECK_NOT_ACTIVE (v4l2element);
/* close device */
close (v4l2element->video_fd);
v4l2element->video_fd = -1;
/* empty lists */
gst_v4l2_empty_lists (v4l2element);
return TRUE;
}
/******************************************************
* gst_v4l2_get_norm()
* Get the norm of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_norm (GstV4l2Element * v4l2element, v4l2_std_id * norm)
{
GST_DEBUG ("getting norm");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_G_STD, norm) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get the current norm for device %s: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_set_norm()
* Set the norm of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_set_norm (GstV4l2Element * v4l2element, v4l2_std_id norm)
{
GST_DEBUG ("trying to set norm to %llx", norm);
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (!GST_V4L2_IS_ACTIVE (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_S_STD, &norm) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to set norm 0x%llx for device %s: %s", norm,
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_get_input()
* Get the input of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_input (GstV4l2Element * v4l2element, gint * input)
{
gint n;
GST_DEBUG ("trying to get input");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_G_INPUT, &n) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get current input on device %s: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
*input = n;
return TRUE;
}
/******************************************************
* gst_v4l2_set_input()
* Set the input of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_set_input (GstV4l2Element * v4l2element, gint input)
{
GST_DEBUG ("trying to set input to %d", input);
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (!GST_V4L2_IS_ACTIVE (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_S_INPUT, &input) < 0) {
GST_WARNING_OBJECT (v4l2element, "Failed to set input %d on device %s: %s",
input, v4l2element->videodev, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_get_output()
* Get the output of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_output (GstV4l2Element * v4l2element, gint * output)
{
gint n;
GST_DEBUG ("trying to get output");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_G_OUTPUT, &n) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get current output on device %s: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
*output = n;
return TRUE;
}
/******************************************************
* gst_v4l2_set_output()
* Set the output of the current device
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_set_output (GstV4l2Element * v4l2element, gint output)
{
GST_DEBUG ("trying to set output to %d", output);
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (!GST_V4L2_IS_ACTIVE (v4l2element))
return FALSE;
if (ioctl (v4l2element->video_fd, VIDIOC_S_OUTPUT, &output) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to set current output on device %s to %d: %s",
v4l2element->videodev, output, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_get_frequency():
* get the current frequency
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_frequency (GstV4l2Element * v4l2element,
gint tunernum, gulong * frequency)
{
struct v4l2_frequency freq;
GstTunerChannel *channel;
GST_DEBUG ("getting current tuner frequency");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
channel = gst_tuner_get_channel (GST_TUNER (v4l2element));
freq.tuner = tunernum;
if (ioctl (v4l2element->video_fd, VIDIOC_G_FREQUENCY, &freq) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get current tuner frequency for device %s: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
*frequency = freq.frequency * channel->freq_multiplicator;
return TRUE;
}
/******************************************************
* gst_v4l2_set_frequency():
* set frequency
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_set_frequency (GstV4l2Element * v4l2element,
gint tunernum, gulong frequency)
{
struct v4l2_frequency freq;
GstTunerChannel *channel;
GST_DEBUG ("setting current tuner frequency to %lu", frequency);
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
if (!GST_V4L2_IS_ACTIVE (v4l2element))
return FALSE;
channel = gst_tuner_get_channel (GST_TUNER (v4l2element));
freq.tuner = tunernum;
/* fill in type - ignore error */
ioctl (v4l2element->video_fd, VIDIOC_G_FREQUENCY, &freq);
freq.frequency = frequency / channel->freq_multiplicator;
if (ioctl (v4l2element->video_fd, VIDIOC_S_FREQUENCY, &freq) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to set current tuner frequency for device %s to %lu: %s",
v4l2element->videodev, frequency, g_strerror (errno));
return FALSE;
}
return TRUE;
}
/******************************************************
* gst_v4l2_signal_strength():
* get the strength of the signal on the current input
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_signal_strength (GstV4l2Element * v4l2element,
gint tunernum, gulong * signal_strength)
{
struct v4l2_tuner tuner;
GST_DEBUG ("trying to get signal strength");
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
tuner.index = tunernum;
if (ioctl (v4l2element->video_fd, VIDIOC_G_TUNER, &tuner) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get signal strength for device %s: %s",
v4l2element->videodev, g_strerror (errno));
return FALSE;
}
*signal_strength = tuner.signal;
return TRUE;
}
/******************************************************
* gst_v4l2_get_attribute():
* try to get the value of one specific attribute
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_get_attribute (GstV4l2Element * v4l2element,
int attribute_num, int *value)
{
struct v4l2_control control;
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
GST_DEBUG ("getting value of attribute %d", attribute_num);
control.id = attribute_num;
if (ioctl (v4l2element->video_fd, VIDIOC_G_CTRL, &control) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to get value for control %d on device %s: %s",
attribute_num, v4l2element->videodev, g_strerror (errno));
return FALSE;
}
*value = control.value;
return TRUE;
}
/******************************************************
* gst_v4l2_set_attribute():
* try to set the value of one specific attribute
* return value: TRUE on success, FALSE on error
******************************************************/
gboolean
gst_v4l2_set_attribute (GstV4l2Element * v4l2element,
int attribute_num, const int value)
{
struct v4l2_control control;
if (!GST_V4L2_IS_OPEN (v4l2element))
return FALSE;
GST_DEBUG ("setting value of attribute %d to %d", attribute_num, value);
control.id = attribute_num;
control.value = value;
if (ioctl (v4l2element->video_fd, VIDIOC_S_CTRL, &control) < 0) {
GST_WARNING_OBJECT (v4l2element,
"Failed to set value %d for control %d on device %s: %s",
value, attribute_num, v4l2element->videodev, g_strerror (errno));
return FALSE;
}
return TRUE;
}