third_party/v4l-utils/lib/include/libv4l2.h

   1 /*
   2 #             (C) 2008 Hans de Goede <hdegoede@redhat.com>
   3
   4 # This program is free software; you can redistribute it and/or modify
   5 # it under the terms of the GNU Lesser General Public License as published by
   6 # the Free Software Foundation; either version 2.1 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Lesser General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Lesser General Public License
  15 # along with this program; if not, write to the Free Software
  16 # Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335  USA
  17 */
  18
  19 #ifndef __LIBV4L2_H
  20 #define __LIBV4L2_H
  21
  22 #include <stdio.h>
  23 #include <unistd.h>
  24 #include <stdint.h>
  25
  26 #ifdef __cplusplus
  27 extern "C" {
  28 #endif /* __cplusplus */
  29
  30 #if HAVE_VISIBILITY
  31 #define LIBV4L_PUBLIC __attribute__ ((visibility("default")))
  32 #else
  33 #define LIBV4L_PUBLIC
  34 #endif
  35
  36 /* Point this to a FILE opened for writing when you want to log error and
  37    status messages to a file, when NULL errors will get send to stderr */
  38 LIBV4L_PUBLIC extern FILE *v4l2_log_file;
  39
  40 /* Just like your regular open/close/etc, except that format conversion is
  41    done if necessary when capturing. That is if you (try to) set a capture
  42    format which is not supported by the cam, but is supported by libv4lconvert,
  43    then the try_fmt / set_fmt will succeed as if the cam supports the format
  44    and on dqbuf / read the data will be converted for you and returned in
  45    the request format. enum_fmt will also report support for the formats to
  46    which conversion is possible.
  47
  48    Another difference is that you can make v4l2_read() calls even on devices
  49    which do not support the regular read() method.
  50
  51    Note the device name passed to v4l2_open must be of a video4linux2 device,
  52    if it is anything else (including a video4linux1 device), v4l2_open will
  53    fail.
  54
  55    Note that the argument to v4l2_ioctl after the request must be a valid
  56    memory address of structure of the appropriate type for the request (for
  57    v4l2 requests which expect a structure address). Passing in NULL or an
  58    invalid memory address will not lead to failure with errno being EFAULT,
  59    as it would with a real ioctl, but will cause libv4l2 to break, and you
  60    get to keep both pieces.
  61 */
  62
  63 LIBV4L_PUBLIC int v4l2_open(const char *file, int oflag, ...);
  64 LIBV4L_PUBLIC int v4l2_close(int fd);
  65 LIBV4L_PUBLIC int v4l2_dup(int fd);
  66 LIBV4L_PUBLIC int v4l2_ioctl(int fd, unsigned long int request, ...);
  67 LIBV4L_PUBLIC ssize_t v4l2_read(int fd, void *buffer, size_t n);
  68 LIBV4L_PUBLIC ssize_t v4l2_write(int fd, const void *buffer, size_t n);
  69 LIBV4L_PUBLIC void *v4l2_mmap(void *start, size_t length, int prot, int flags,
  70                 int fd, int64_t offset);
  71 LIBV4L_PUBLIC int v4l2_munmap(void *_start, size_t length);
  72
  73
  74 /* Misc utility functions */
  75
  76 /* This function takes a value of 0 - 65535, and then scales that range to
  77    the actual range of the given v4l control id, and then if the cid exists
  78    and is not locked sets the cid to the scaled value.
  79
  80    Normally returns 0, even if the cid did not exist or was locked, returns
  81    non 0 when an other error occured. */
  82 LIBV4L_PUBLIC int v4l2_set_control(int fd, int cid, int value);
  83
  84 /* This function returns a value of 0 - 65535, scaled to from the actual range
  85    of the given v4l control id. When the cid does not exist, or could not be
  86    accessed -1 is returned. */
  87 LIBV4L_PUBLIC int v4l2_get_control(int fd, int cid);
  88
  89
  90 /* "low level" access functions, these functions allow somewhat lower level
  91    access to libv4l2 (currently there only is v4l2_fd_open here) */
  92
  93 /* Flags for v4l2_fd_open's v4l2_flags argument */
  94
  95 /* Disable all format conversion done by libv4l2, this includes the software
  96    whitebalance, gamma correction, flipping, etc. libv4lconvert does. Use this
  97    if you want raw frame data, but still want the additional error checks and
  98    the read() emulation libv4l2 offers. */
  99 #define V4L2_DISABLE_CONVERSION 0x01
 100 /* This flag is *OBSOLETE*, since version 0.5.98 libv4l *always* reports
 101    emulated formats to ENUM_FMT, except when conversion is disabled. */
 102 #define V4L2_ENABLE_ENUM_FMT_EMULATION 0x02
 103
 104 /* v4l2_fd_open: open an already opened fd for further use through
 105    v4l2lib and possibly modify libv4l2's default behavior through the
 106    v4l2_flags argument.
 107
 108    Returns fd on success, -1 if the fd is not suitable for use through libv4l2
 109    (note the fd is left open in this case). */
 110 LIBV4L_PUBLIC int v4l2_fd_open(int fd, int v4l2_flags);
 111
 112 #ifdef __cplusplus
 113 }
 114 #endif /* __cplusplus */
 115
 116 #endif