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Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-queryctrl.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-queryctrl.rst | 975 |
1 files changed, 348 insertions, 627 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst index f3ce0ab53bae..82769de801b1 100644 --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst @@ -105,116 +105,71 @@ See also the examples in :ref:`control`. :stub-columns: 0 :widths: 1 1 2 - - - .. row 1 - - - __u32 - - - ``id`` - - - Identifies the control, set by the application. See - :ref:`control-id` for predefined IDs. When the ID is ORed with - V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and - returns the first control with a higher ID. Drivers which do not - support this flag yet always return an ``EINVAL`` error code. - - - .. row 2 - - - __u32 - - - ``type`` - - - Type of control, see :c:type:`v4l2_ctrl_type`. - - - .. row 3 - - - __u8 - - - ``name``\ [32] - - - Name of the control, a NUL-terminated ASCII string. This - information is intended for the user. - - - .. row 4 - - - __s32 - - - ``minimum`` - - - Minimum value, inclusive. This field gives a lower bound for the - control. See enum :c:type:`v4l2_ctrl_type` how - the minimum value is to be used for each possible control type. - Note that this a signed 32-bit value. - - - .. row 5 - - - __s32 - - - ``maximum`` - - - Maximum value, inclusive. This field gives an upper bound for the - control. See enum :c:type:`v4l2_ctrl_type` how - the maximum value is to be used for each possible control type. - Note that this a signed 32-bit value. - - - .. row 6 - - - __s32 - - - ``step`` - - - This field gives a step size for the control. See enum - :c:type:`v4l2_ctrl_type` how the step value is - to be used for each possible control type. Note that this an - unsigned 32-bit value. - - Generally drivers should not scale hardware control values. It may - be necessary for example when the ``name`` or ``id`` imply a - particular unit and the hardware actually accepts only multiples - of said unit. If so, drivers must take care values are properly - rounded when scaling, such that errors will not accumulate on - repeated read-write cycles. - - This field gives the smallest change of an integer control - actually affecting hardware. Often the information is needed when - the user can change controls by keyboard or GUI buttons, rather - than a slider. When for example a hardware register accepts values - 0-511 and the driver reports 0-65535, step should be 128. - - Note that although signed, the step value is supposed to be always - positive. - - - .. row 7 - - - __s32 - - - ``default_value`` - - - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_BOOLEAN``, - ``_BITMASK``, ``_MENU`` or ``_INTEGER_MENU`` control. Not valid - for other types of controls. - - .. note:: - - Drivers reset controls to their default value only when - the driver is first loaded, never afterwards. - - - .. row 8 - - - __u32 - - - ``flags`` - - - Control flags, see :ref:`control-flags`. - - - .. row 9 - - - __u32 - - - ``reserved``\ [2] - - - Reserved for future extensions. Drivers must set the array to - zero. + * - __u32 + - ``id`` + - Identifies the control, set by the application. See + :ref:`control-id` for predefined IDs. When the ID is ORed with + V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and + returns the first control with a higher ID. Drivers which do not + support this flag yet always return an ``EINVAL`` error code. + * - __u32 + - ``type`` + - Type of control, see :c:type:`v4l2_ctrl_type`. + * - __u8 + - ``name``\ [32] + - Name of the control, a NUL-terminated ASCII string. This + information is intended for the user. + * - __s32 + - ``minimum`` + - Minimum value, inclusive. This field gives a lower bound for the + control. See enum :c:type:`v4l2_ctrl_type` how + the minimum value is to be used for each possible control type. + Note that this a signed 32-bit value. + * - __s32 + - ``maximum`` + - Maximum value, inclusive. This field gives an upper bound for the + control. See enum :c:type:`v4l2_ctrl_type` how + the maximum value is to be used for each possible control type. + Note that this a signed 32-bit value. + * - __s32 + - ``step`` + - This field gives a step size for the control. See enum + :c:type:`v4l2_ctrl_type` how the step value is + to be used for each possible control type. Note that this an + unsigned 32-bit value. + + Generally drivers should not scale hardware control values. It may + be necessary for example when the ``name`` or ``id`` imply a + particular unit and the hardware actually accepts only multiples + of said unit. If so, drivers must take care values are properly + rounded when scaling, such that errors will not accumulate on + repeated read-write cycles. + + This field gives the smallest change of an integer control + actually affecting hardware. Often the information is needed when + the user can change controls by keyboard or GUI buttons, rather + than a slider. When for example a hardware register accepts values + 0-511 and the driver reports 0-65535, step should be 128. + + Note that although signed, the step value is supposed to be always + positive. + * - __s32 + - ``default_value`` + - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_BOOLEAN``, + ``_BITMASK``, ``_MENU`` or ``_INTEGER_MENU`` control. Not valid + for other types of controls. + + .. note:: + + Drivers reset controls to their default value only when + the driver is first loaded, never afterwards. + * - __u32 + - ``flags`` + - Control flags, see :ref:`control-flags`. + * - __u32 + - ``reserved``\ [2] + - Reserved for future extensions. Drivers must set the array to + zero. @@ -229,158 +184,93 @@ See also the examples in :ref:`control`. :stub-columns: 0 :widths: 1 1 2 - - - .. row 1 - - - __u32 - - - ``id`` - - - Identifies the control, set by the application. See - :ref:`control-id` for predefined IDs. When the ID is ORed with - ``V4L2_CTRL_FLAG_NEXT_CTRL`` the driver clears the flag and - returns the first non-compound control with a higher ID. When the - ID is ORed with ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` the driver clears - the flag and returns the first compound control with a higher ID. - Set both to get the first control (compound or not) with a higher - ID. - - - .. row 2 - - - __u32 - - - ``type`` - - - Type of control, see :c:type:`v4l2_ctrl_type`. - - - .. row 3 - - - char - - - ``name``\ [32] - - - Name of the control, a NUL-terminated ASCII string. This - information is intended for the user. - - - .. row 4 - - - __s64 - - - ``minimum`` - - - Minimum value, inclusive. This field gives a lower bound for the - control. See enum :c:type:`v4l2_ctrl_type` how - the minimum value is to be used for each possible control type. - Note that this a signed 64-bit value. - - - .. row 5 - - - __s64 - - - ``maximum`` - - - Maximum value, inclusive. This field gives an upper bound for the - control. See enum :c:type:`v4l2_ctrl_type` how - the maximum value is to be used for each possible control type. - Note that this a signed 64-bit value. - - - .. row 6 - - - __u64 - - - ``step`` - - - This field gives a step size for the control. See enum - :c:type:`v4l2_ctrl_type` how the step value is - to be used for each possible control type. Note that this an - unsigned 64-bit value. - - Generally drivers should not scale hardware control values. It may - be necessary for example when the ``name`` or ``id`` imply a - particular unit and the hardware actually accepts only multiples - of said unit. If so, drivers must take care values are properly - rounded when scaling, such that errors will not accumulate on - repeated read-write cycles. - - This field gives the smallest change of an integer control - actually affecting hardware. Often the information is needed when - the user can change controls by keyboard or GUI buttons, rather - than a slider. When for example a hardware register accepts values - 0-511 and the driver reports 0-65535, step should be 128. - - - .. row 7 - - - __s64 - - - ``default_value`` - - - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_INTEGER64``, - ``_BOOLEAN``, ``_BITMASK``, ``_MENU``, ``_INTEGER_MENU``, ``_U8`` - or ``_U16`` control. Not valid for other types of controls. - - .. note:: - - Drivers reset controls to their default value only when - the driver is first loaded, never afterwards. - - - .. row 8 - - - __u32 - - - ``flags`` - - - Control flags, see :ref:`control-flags`. - - - .. row 9 - - - __u32 - - - ``elem_size`` - - - The size in bytes of a single element of the array. Given a char - pointer ``p`` to a 3-dimensional array you can find the position - of cell ``(z, y, x)`` as follows: - ``p + ((z * dims[1] + y) * dims[0] + x) * elem_size``. - ``elem_size`` is always valid, also when the control isn't an - array. For string controls ``elem_size`` is equal to - ``maximum + 1``. - - - .. row 10 - - - __u32 - - - ``elems`` - - - The number of elements in the N-dimensional array. If this control - is not an array, then ``elems`` is 1. The ``elems`` field can - never be 0. - - - .. row 11 - - - __u32 - - - ``nr_of_dims`` - - - The number of dimension in the N-dimensional array. If this - control is not an array, then this field is 0. - - - .. row 12 - - - __u32 - - - ``dims[V4L2_CTRL_MAX_DIMS]`` - - - The size of each dimension. The first ``nr_of_dims`` elements of - this array must be non-zero, all remaining elements must be zero. - - - .. row 13 - - - __u32 - - - ``reserved``\ [32] - - - Reserved for future extensions. Applications and drivers must set - the array to zero. + * - __u32 + - ``id`` + - Identifies the control, set by the application. See + :ref:`control-id` for predefined IDs. When the ID is ORed with + ``V4L2_CTRL_FLAG_NEXT_CTRL`` the driver clears the flag and + returns the first non-compound control with a higher ID. When the + ID is ORed with ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` the driver clears + the flag and returns the first compound control with a higher ID. + Set both to get the first control (compound or not) with a higher + ID. + * - __u32 + - ``type`` + - Type of control, see :c:type:`v4l2_ctrl_type`. + * - char + - ``name``\ [32] + - Name of the control, a NUL-terminated ASCII string. This + information is intended for the user. + * - __s64 + - ``minimum`` + - Minimum value, inclusive. This field gives a lower bound for the + control. See enum :c:type:`v4l2_ctrl_type` how + the minimum value is to be used for each possible control type. + Note that this a signed 64-bit value. + * - __s64 + - ``maximum`` + - Maximum value, inclusive. This field gives an upper bound for the + control. See enum :c:type:`v4l2_ctrl_type` how + the maximum value is to be used for each possible control type. + Note that this a signed 64-bit value. + * - __u64 + - ``step`` + - This field gives a step size for the control. See enum + :c:type:`v4l2_ctrl_type` how the step value is + to be used for each possible control type. Note that this an + unsigned 64-bit value. + + Generally drivers should not scale hardware control values. It may + be necessary for example when the ``name`` or ``id`` imply a + particular unit and the hardware actually accepts only multiples + of said unit. If so, drivers must take care values are properly + rounded when scaling, such that errors will not accumulate on + repeated read-write cycles. + + This field gives the smallest change of an integer control + actually affecting hardware. Often the information is needed when + the user can change controls by keyboard or GUI buttons, rather + than a slider. When for example a hardware register accepts values + 0-511 and the driver reports 0-65535, step should be 128. + * - __s64 + - ``default_value`` + - The default value of a ``V4L2_CTRL_TYPE_INTEGER``, ``_INTEGER64``, + ``_BOOLEAN``, ``_BITMASK``, ``_MENU``, ``_INTEGER_MENU``, ``_U8`` + or ``_U16`` control. Not valid for other types of controls. + + .. note:: + + Drivers reset controls to their default value only when + the driver is first loaded, never afterwards. + * - __u32 + - ``flags`` + - Control flags, see :ref:`control-flags`. + * - __u32 + - ``elem_size`` + - The size in bytes of a single element of the array. Given a char + pointer ``p`` to a 3-dimensional array you can find the position + of cell ``(z, y, x)`` as follows: + ``p + ((z * dims[1] + y) * dims[0] + x) * elem_size``. + ``elem_size`` is always valid, also when the control isn't an + array. For string controls ``elem_size`` is equal to + ``maximum + 1``. + * - __u32 + - ``elems`` + - The number of elements in the N-dimensional array. If this control + is not an array, then ``elems`` is 1. The ``elems`` field can + never be 0. + * - __u32 + - ``nr_of_dims`` + - The number of dimension in the N-dimensional array. If this + control is not an array, then this field is 0. + * - __u32 + - ``dims[V4L2_CTRL_MAX_DIMS]`` + - The size of each dimension. The first ``nr_of_dims`` elements of + this array must be non-zero, all remaining elements must be zero. + * - __u32 + - ``reserved``\ [32] + - Reserved for future extensions. Applications and drivers must set + the array to zero. @@ -393,64 +283,35 @@ See also the examples in :ref:`control`. :stub-columns: 0 :widths: 1 1 2 1 - - - .. row 1 - - - __u32 - - - - - ``id`` - - - Identifies the control, set by the application from the respective - struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``id``. - - - .. row 2 - - - __u32 - - - - - ``index`` - - - Index of the menu item, starting at zero, set by the application. - - - .. row 3 - - - union - - - - - - - - - - .. row 4 - - - - - __u8 - - - ``name``\ [32] - - - Name of the menu item, a NUL-terminated ASCII string. This - information is intended for the user. This field is valid for - ``V4L2_CTRL_FLAG_MENU`` type controls. - - - .. row 5 - - - - - __s64 - - - ``value`` - - - Value of the integer menu item. This field is valid for - ``V4L2_CTRL_FLAG_INTEGER_MENU`` type controls. - - - .. row 6 - - - __u32 - - - - - ``reserved`` - - - Reserved for future extensions. Drivers must set the array to - zero. + * - __u32 + - + - ``id`` + - Identifies the control, set by the application from the respective + struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` ``id``. + * - __u32 + - + - ``index`` + - Index of the menu item, starting at zero, set by the application. + * - union + - + - + - + * - + - __u8 + - ``name``\ [32] + - Name of the menu item, a NUL-terminated ASCII string. This + information is intended for the user. This field is valid for + ``V4L2_CTRL_FLAG_MENU`` type controls. + * - + - __s64 + - ``value`` + - Value of the integer menu item. This field is valid for + ``V4L2_CTRL_FLAG_INTEGER_MENU`` type controls. + * - __u32 + - + - ``reserved`` + - Reserved for future extensions. Drivers must set the array to + zero. @@ -465,193 +326,102 @@ See also the examples in :ref:`control`. :stub-columns: 0 :widths: 30 5 5 5 55 - - - .. row 1 - - - Type - - - ``minimum`` - - - ``step`` - - - ``maximum`` - - - Description - - - .. row 2 - - - ``V4L2_CTRL_TYPE_INTEGER`` - - - any - - - any - - - any - - - An integer-valued control ranging from minimum to maximum - inclusive. The step value indicates the increment between values. - - - .. row 3 - - - ``V4L2_CTRL_TYPE_BOOLEAN`` - - - 0 - - - 1 - - - 1 - - - A boolean-valued control. Zero corresponds to "disabled", and one - means "enabled". - - - .. row 4 - - - ``V4L2_CTRL_TYPE_MENU`` - - - ≥ 0 - - - 1 - - - N-1 - - - The control has a menu of N choices. The names of the menu items - can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. - - - .. row 5 - - - ``V4L2_CTRL_TYPE_INTEGER_MENU`` - - - ≥ 0 - - - 1 - - - N-1 - - - The control has a menu of N choices. The values of the menu items - can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. This is - similar to ``V4L2_CTRL_TYPE_MENU`` except that instead of strings, - the menu items are signed 64-bit integers. - - - .. row 6 - - - ``V4L2_CTRL_TYPE_BITMASK`` - - - 0 - - - n/a - - - any - - - A bitmask field. The maximum value is the set of bits that can be - used, all other bits are to be 0. The maximum value is interpreted - as a __u32, allowing the use of bit 31 in the bitmask. - - - .. row 7 - - - ``V4L2_CTRL_TYPE_BUTTON`` - - - 0 - - - 0 - - - 0 - - - A control which performs an action when set. Drivers must ignore - the value passed with ``VIDIOC_S_CTRL`` and return an ``EINVAL`` error - code on a ``VIDIOC_G_CTRL`` attempt. - - - .. row 8 - - - ``V4L2_CTRL_TYPE_INTEGER64`` - - - any - - - any - - - any - - - A 64-bit integer valued control. Minimum, maximum and step size - cannot be queried using ``VIDIOC_QUERYCTRL``. Only - ``VIDIOC_QUERY_EXT_CTRL`` can retrieve the 64-bit min/max/step - values, they should be interpreted as n/a when using - ``VIDIOC_QUERYCTRL``. - - - .. row 9 - - - ``V4L2_CTRL_TYPE_STRING`` - - - ≥ 0 - - - ≥ 1 - - - ≥ 0 - - - The minimum and maximum string lengths. The step size means that - the string must be (minimum + N * step) characters long for N ≥ 0. - These lengths do not include the terminating zero, so in order to - pass a string of length 8 to - :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you need to - set the ``size`` field of struct - :c:type:`v4l2_ext_control` to 9. For - :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you can set - the ``size`` field to ``maximum`` + 1. Which character encoding is - used will depend on the string control itself and should be part - of the control documentation. - - - .. row 10 - - - ``V4L2_CTRL_TYPE_CTRL_CLASS`` - - - n/a - - - n/a - - - n/a - - - This is not a control. When ``VIDIOC_QUERYCTRL`` is called with a - control ID equal to a control class code (see :ref:`ctrl-class`) - + 1, the ioctl returns the name of the control class and this - control type. Older drivers which do not support this feature - return an ``EINVAL`` error code. - - - .. row 11 - - - ``V4L2_CTRL_TYPE_U8`` - - - any - - - any - - - any - - - An unsigned 8-bit valued control ranging from minimum to maximum - inclusive. The step value indicates the increment between values. - - - .. row 12 - - - ``V4L2_CTRL_TYPE_U16`` - - - any - - - any - - - any - - - An unsigned 16-bit valued control ranging from minimum to maximum - inclusive. The step value indicates the increment between values. - - - .. row 13 - - - ``V4L2_CTRL_TYPE_U32`` - - - any - - - any - - - any - - - An unsigned 32-bit valued control ranging from minimum to maximum - inclusive. The step value indicates the increment between values. + * - Type + - ``minimum`` + - ``step`` + - ``maximum`` + - Description + * - ``V4L2_CTRL_TYPE_INTEGER`` + - any + - any + - any + - An integer-valued control ranging from minimum to maximum + inclusive. The step value indicates the increment between values. + * - ``V4L2_CTRL_TYPE_BOOLEAN`` + - 0 + - 1 + - 1 + - A boolean-valued control. Zero corresponds to "disabled", and one + means "enabled". + * - ``V4L2_CTRL_TYPE_MENU`` + - ≥ 0 + - 1 + - N-1 + - The control has a menu of N choices. The names of the menu items + can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. + * - ``V4L2_CTRL_TYPE_INTEGER_MENU`` + - ≥ 0 + - 1 + - N-1 + - The control has a menu of N choices. The values of the menu items + can be enumerated with the ``VIDIOC_QUERYMENU`` ioctl. This is + similar to ``V4L2_CTRL_TYPE_MENU`` except that instead of strings, + the menu items are signed 64-bit integers. + * - ``V4L2_CTRL_TYPE_BITMASK`` + - 0 + - n/a + - any + - A bitmask field. The maximum value is the set of bits that can be + used, all other bits are to be 0. The maximum value is interpreted + as a __u32, allowing the use of bit 31 in the bitmask. + * - ``V4L2_CTRL_TYPE_BUTTON`` + - 0 + - 0 + - 0 + - A control which performs an action when set. Drivers must ignore + the value passed with ``VIDIOC_S_CTRL`` and return an ``EINVAL`` error + code on a ``VIDIOC_G_CTRL`` attempt. + * - ``V4L2_CTRL_TYPE_INTEGER64`` + - any + - any + - any + - A 64-bit integer valued control. Minimum, maximum and step size + cannot be queried using ``VIDIOC_QUERYCTRL``. Only + ``VIDIOC_QUERY_EXT_CTRL`` can retrieve the 64-bit min/max/step + values, they should be interpreted as n/a when using + ``VIDIOC_QUERYCTRL``. + * - ``V4L2_CTRL_TYPE_STRING`` + - ≥ 0 + - ≥ 1 + - ≥ 0 + - The minimum and maximum string lengths. The step size means that + the string must be (minimum + N * step) characters long for N ≥ 0. + These lengths do not include the terminating zero, so in order to + pass a string of length 8 to + :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you need to + set the ``size`` field of struct + :c:type:`v4l2_ext_control` to 9. For + :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` you can set + the ``size`` field to ``maximum`` + 1. Which character encoding is + used will depend on the string control itself and should be part + of the control documentation. + * - ``V4L2_CTRL_TYPE_CTRL_CLASS`` + - n/a + - n/a + - n/a + - This is not a control. When ``VIDIOC_QUERYCTRL`` is called with a + control ID equal to a control class code (see :ref:`ctrl-class`) + + 1, the ioctl returns the name of the control class and this + control type. Older drivers which do not support this feature + return an ``EINVAL`` error code. + * - ``V4L2_CTRL_TYPE_U8`` + - any + - any + - any + - An unsigned 8-bit valued control ranging from minimum to maximum + inclusive. The step value indicates the increment between values. + * - ``V4L2_CTRL_TYPE_U16`` + - any + - any + - any + - An unsigned 16-bit valued control ranging from minimum to maximum + inclusive. The step value indicates the increment between values. + * - ``V4L2_CTRL_TYPE_U32`` + - any + - any + - any + - An unsigned 32-bit valued control ranging from minimum to maximum + inclusive. The step value indicates the increment between values. @@ -666,126 +436,77 @@ See also the examples in :ref:`control`. :stub-columns: 0 :widths: 3 1 4 - - - .. row 1 - - - ``V4L2_CTRL_FLAG_DISABLED`` - - - 0x0001 - - - This control is permanently disabled and should be ignored by the - application. Any attempt to change the control will result in an - ``EINVAL`` error code. - - - .. row 2 - - - ``V4L2_CTRL_FLAG_GRABBED`` - - - 0x0002 - - - This control is temporarily unchangeable, for example because - another application took over control of the respective resource. - Such controls may be displayed specially in a user interface. - Attempts to change the control may result in an ``EBUSY`` error code. - - - .. row 3 - - - ``V4L2_CTRL_FLAG_READ_ONLY`` - - - 0x0004 - - - This control is permanently readable only. Any attempt to change - the control will result in an ``EINVAL`` error code. - - - .. row 4 - - - ``V4L2_CTRL_FLAG_UPDATE`` - - - 0x0008 - - - A hint that changing this control may affect the value of other - controls within the same control class. Applications should update - their user interface accordingly. - - - .. row 5 - - - ``V4L2_CTRL_FLAG_INACTIVE`` - - - 0x0010 - - - This control is not applicable to the current configuration and - should be displayed accordingly in a user interface. For example - the flag may be set on a MPEG audio level 2 bitrate control when - MPEG audio encoding level 1 was selected with another control. - - - .. row 6 - - - ``V4L2_CTRL_FLAG_SLIDER`` - - - 0x0020 - - - A hint that this control is best represented as a slider-like - element in a user interface. - - - .. row 7 - - - ``V4L2_CTRL_FLAG_WRITE_ONLY`` - - - 0x0040 - - - This control is permanently writable only. Any attempt to read the - control will result in an ``EACCES`` error code error code. This flag - is typically present for relative controls or action controls - where writing a value will cause the device to carry out a given - action (e. g. motor control) but no meaningful value can be - returned. - - - .. row 8 - - - ``V4L2_CTRL_FLAG_VOLATILE`` - - - 0x0080 - - - This control is volatile, which means that the value of the - control changes continuously. A typical example would be the - current gain value if the device is in auto-gain mode. In such a - case the hardware calculates the gain value based on the lighting - conditions which can change over time. - - .. note:: - - Setting a new value for a volatile control will be ignored - unless - :ref:`V4L2_CTRL_FLAG_EXECUTE_ON_WRITE <FLAG_EXECUTE_ON_WRITE>` - is also set. - Setting a new value for a volatile control will *never* trigger a - :ref:`V4L2_EVENT_CTRL_CH_VALUE <ctrl-changes-flags>` event. - - - .. row 9 - - - ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` - - - 0x0100 - - - This control has a pointer type, so its value has to be accessed - using one of the pointer fields of struct - :c:type:`v4l2_ext_control`. This flag is set - for controls that are an array, string, or have a compound type. - In all cases you have to set a pointer to memory containing the - payload of the control. - - - .. row 10 - .. _FLAG_EXECUTE_ON_WRITE: - - - ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` - - - 0x0200 - - - The value provided to the control will be propagated to the driver - even if it remains constant. This is required when the control - represents an action on the hardware. For example: clearing an - error flag or triggering the flash. All the controls of the type - ``V4L2_CTRL_TYPE_BUTTON`` have this flag set. + * - ``V4L2_CTRL_FLAG_DISABLED`` + - 0x0001 + - This control is permanently disabled and should be ignored by the + application. Any attempt to change the control will result in an + ``EINVAL`` error code. + * - ``V4L2_CTRL_FLAG_GRABBED`` + - 0x0002 + - This control is temporarily unchangeable, for example because + another application took over control of the respective resource. + Such controls may be displayed specially in a user interface. + Attempts to change the control may result in an ``EBUSY`` error code. + * - ``V4L2_CTRL_FLAG_READ_ONLY`` + - 0x0004 + - This control is permanently readable only. Any attempt to change + the control will result in an ``EINVAL`` error code. + * - ``V4L2_CTRL_FLAG_UPDATE`` + - 0x0008 + - A hint that changing this control may affect the value of other + controls within the same control class. Applications should update + their user interface accordingly. + * - ``V4L2_CTRL_FLAG_INACTIVE`` + - 0x0010 + - This control is not applicable to the current configuration and + should be displayed accordingly in a user interface. For example + the flag may be set on a MPEG audio level 2 bitrate control when + MPEG audio encoding level 1 was selected with another control. + * - ``V4L2_CTRL_FLAG_SLIDER`` + - 0x0020 + - A hint that this control is best represented as a slider-like + element in a user interface. + * - ``V4L2_CTRL_FLAG_WRITE_ONLY`` + - 0x0040 + - This control is permanently writable only. Any attempt to read the + control will result in an ``EACCES`` error code error code. This flag + is typically present for relative controls or action controls + where writing a value will cause the device to carry out a given + action (e. g. motor control) but no meaningful value can be + returned. + * - ``V4L2_CTRL_FLAG_VOLATILE`` + - 0x0080 + - This control is volatile, which means that the value of the + control changes continuously. A typical example would be the + current gain value if the device is in auto-gain mode. In such a + case the hardware calculates the gain value based on the lighting + conditions which can change over time. + + .. note:: + + Setting a new value for a volatile control will be ignored + unless + :ref:`V4L2_CTRL_FLAG_EXECUTE_ON_WRITE <FLAG_EXECUTE_ON_WRITE>` + is also set. + Setting a new value for a volatile control will *never* trigger a + :ref:`V4L2_EVENT_CTRL_CH_VALUE <ctrl-changes-flags>` event. + * - ``V4L2_CTRL_FLAG_HAS_PAYLOAD`` + - 0x0100 + - This control has a pointer type, so its value has to be accessed + using one of the pointer fields of struct + :c:type:`v4l2_ext_control`. This flag is set + for controls that are an array, string, or have a compound type. + In all cases you have to set a pointer to memory containing the + payload of the control. + * .. _FLAG_EXECUTE_ON_WRITE: + + - ``V4L2_CTRL_FLAG_EXECUTE_ON_WRITE`` + - 0x0200 + - The value provided to the control will be propagated to the driver + even if it remains constant. This is required when the control + represents an action on the hardware. For example: clearing an + error flag or triggering the flash. All the controls of the type + ``V4L2_CTRL_TYPE_BUTTON`` have this flag set. Return Value |