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Diffstat (limited to 'Documentation/media/uapi/v4l/libv4l-introduction.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/libv4l-introduction.rst | 77 |
1 files changed, 46 insertions, 31 deletions
diff --git a/Documentation/media/uapi/v4l/libv4l-introduction.rst b/Documentation/media/uapi/v4l/libv4l-introduction.rst index 61d085f..ccc3c4d 100644 --- a/Documentation/media/uapi/v4l/libv4l-introduction.rst +++ b/Documentation/media/uapi/v4l/libv4l-introduction.rst @@ -113,56 +113,71 @@ Libv4l device control functions The common file operation methods are provided by libv4l. -Those functions operate just like glibc -open/close/dup/ioctl/read/mmap/munmap: +Those functions operate just like the gcc function ``dup()`` and +V4L2 functions +:c:func:`open() <v4l2-open>`, :c:func:`close() <v4l2-close>`, +:c:func:`ioctl() <v4l2-ioctl>`, :c:func:`read() <v4l2-read>`, +:c:func:`mmap() <v4l2-mmap>` and :c:func:`munmap() <v4l2-munmap>`: -- :c:type:`int v4l2_open(const char *file, int oflag, ...)` - operates like the - standard :ref:`open() <func-open>` function. +.. c:function:: int v4l2_open(const char *file, int oflag, ...) -- :c:type:`int v4l2_close(int fd)` - operates like the standard - :ref:`close() <func-close>` function. + operates like the :c:func:`open() <v4l2-open>` function. -- :c:type:`int v4l2_dup(int fd)` - operates like the standard dup() function, - duplicating a file handler. +.. c:function:: int v4l2_close(int fd) -- :c:type:`int v4l2_ioctl (int fd, unsigned long int request, ...)` - operates - like the standard :ref:`ioctl() <func-ioctl>` function. + operates like the :c:func:`close() <v4l2-close>` function. -- :c:type:`int v4l2_read (int fd, void* buffer, size_t n)` - operates like the - standard :ref:`read() <func-read>` function. +.. c:function:: int v4l2_dup(int fd) -- :c:type:`void v4l2_mmap(void *start, size_t length, int prot, int flags, int - fd, int64_t offset);` - operates like the standard - :ref:`mmap() <func-mmap>` function. + operates like the libc ``dup()`` function, duplicating a file handler. -- :c:type:`int v4l2_munmap(void *_start, size_t length);` - operates like the - standard :ref:`munmap() <func-munmap>` function. +.. c:function:: int v4l2_ioctl (int fd, unsigned long int request, ...) + + operates like the :c:func:`ioctl() <v4l2-ioctl>` function. + +.. c:function:: int v4l2_read (int fd, void* buffer, size_t n) + + operates like the :c:func:`read() <v4l2-read>` function. + +.. c:function:: void v4l2_mmap(void *start, size_t length, int prot, int flags, int fd, int64_t offset); + + operates like the :c:func:`munmap() <v4l2-munmap>` function. + +.. c:function:: int v4l2_munmap(void *_start, size_t length); + + operates like the :c:func:`munmap() <v4l2-munmap>` function. Those functions provide additional control: -- :c:type:`int v4l2_fd_open(int fd, int v4l2_flags)` - opens an already opened - fd for further use through v4l2lib and possibly modify libv4l2's - default behavior through the v4l2_flags argument. Currently, - v4l2_flags can be ``V4L2_DISABLE_CONVERSION``, to disable format - conversion. +.. c:function:: int v4l2_fd_open(int fd, int v4l2_flags) + + opens an already opened fd for further use through v4l2lib and possibly + modify libv4l2's default behavior through the ``v4l2_flags`` argument. + Currently, ``v4l2_flags`` can be ``V4L2_DISABLE_CONVERSION``, to disable + format conversion. -- :c:type:`int v4l2_set_control(int fd, int cid, int value)` - This function - takes a value of 0 - 65535, and then scales that range to the actual - range of the given v4l control id, and then if the cid exists and is +.. c:function:: int v4l2_set_control(int fd, int cid, int value) + + This function takes a value of 0 - 65535, and then scales that range to the + actual range of the given v4l control id, and then if the cid exists and is not locked sets the cid to the scaled value. -- :c:type:`int v4l2_get_control(int fd, int cid)` - This function returns a - value of 0 - 65535, scaled to from the actual range of the given v4l - control id. when the cid does not exist, could not be accessed for - some reason, or some error occurred 0 is returned. +.. c:function:: int v4l2_get_control(int fd, int cid) + + This function returns a value of 0 - 65535, scaled to from the actual range + of the given v4l control id. when the cid does not exist, could not be + accessed for some reason, or some error occurred 0 is returned. v4l1compat.so wrapper library ============================= -This library intercepts calls to open/close/ioctl/mmap/mmunmap +This library intercepts calls to +:c:func:`open() <v4l2-open>`, :c:func:`close() <v4l2-close>`, +:c:func:`ioctl() <v4l2-ioctl>`, :c:func:`mmap() <v4l2-mmap>` and +:c:func:`munmap() <v4l2-munmap>` operations and redirects them to the libv4l counterparts, by using -LD_PRELOAD=/usr/lib/v4l1compat.so. It also emulates V4L1 calls via V4L2 +``LD_PRELOAD=/usr/lib/v4l1compat.so``. It also emulates V4L1 calls via V4L2 API. It allows usage of binary legacy applications that still don't use |