diff options
Diffstat (limited to 'Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst | 42 |
1 files changed, 18 insertions, 24 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst index e5c4e0a175a7..c50a76c70491 100644 --- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst @@ -138,11 +138,12 @@ still cause this situation. - Identifies the control, set by the application. * - __u32 - ``size`` - - The total size in bytes of the payload of this control. This is - normally 0, but for pointer controls this should be set to the - size of the memory containing the payload, or that will receive - the payload. If :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` finds that this value is - less than is required to store the payload result, then it is set + - The total size in bytes of the payload of this control. + * - :cspan:`2` The ``size`` field is normally 0, but for pointer + controls this should be set to the size of the memory that contains + the payload or that will receive the payload. + If :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` finds that this value + is less than is required to store the payload result, then it is set to a value large enough to store the payload result and ``ENOSPC`` is returned. @@ -247,29 +248,18 @@ still cause this situation. * - union { - (anonymous) * - __u32 - - ``ctrl_class`` - - The control class to which all controls belong, see - :ref:`ctrl-class`. Drivers that use a kernel framework for - handling controls will also accept a value of 0 here, meaning that - the controls can belong to any control class. Whether drivers - support this can be tested by setting ``ctrl_class`` to 0 and - calling :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with a ``count`` of 0. If that - succeeds, then the driver supports this feature. - * - __u32 - ``which`` - Which value of the control to get/set/try. - ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of the - control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default + * - :cspan:`2` ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of + the control, ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default value of the control and ``V4L2_CTRL_WHICH_REQUEST_VAL`` indicates that these controls have to be retrieved from a request or tried/set for a request. In the latter case the ``request_fd`` field contains the file descriptor of the request that should be used. If the device does not support requests, then ``EACCES`` will be returned. - .. note:: - - When using ``V4L2_CTRL_WHICH_DEF_VAL`` be aware that you can only - get the default value of the control, you cannot set or try it. + When using ``V4L2_CTRL_WHICH_DEF_VAL`` be aware that you can only + get the default value of the control, you cannot set or try it. For backwards compatibility you can also use a control class here (see :ref:`ctrl-class`). In that case all controls have to @@ -277,9 +267,12 @@ still cause this situation. just use ``V4L2_CTRL_WHICH_CUR_VAL``. There are some very old drivers that do not yet support ``V4L2_CTRL_WHICH_CUR_VAL`` and that require a control class here. You can test for such drivers - by setting ctrl_class to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling - VIDIOC_TRY_EXT_CTRLS with a count of 0. If that fails, then the - driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``. + by setting ``which`` to ``V4L2_CTRL_WHICH_CUR_VAL`` and calling + :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with a count of 0. + If that fails, then the driver does not support ``V4L2_CTRL_WHICH_CUR_VAL``. + * - __u32 + - ``ctrl_class`` + - Deprecated name kept for backwards compatibility. Use ``which`` instead. * - } - * - __u32 @@ -287,7 +280,8 @@ still cause this situation. - The number of controls in the controls array. May also be zero. * - __u32 - ``error_idx`` - - Set by the driver in case of an error. If the error is associated + - Index of the failing control. Set by the driver in case of an error. + * - :cspan:`2` If the error is associated with a particular control, then ``error_idx`` is set to the index of that control. If the error is not related to a specific control, or the validation step failed (see below), then |