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diff --git a/Documentation/media/uapi/v4l/control.rst b/Documentation/media/uapi/v4l/control.rst deleted file mode 100644 index ef62e088ff7a..000000000000 --- a/Documentation/media/uapi/v4l/control.rst +++ /dev/null @@ -1,512 +0,0 @@ -.. Permission is granted to copy, distribute and/or modify this -.. document under the terms of the GNU Free Documentation License, -.. Version 1.1 or any later version published by the Free Software -.. Foundation, with no Invariant Sections, no Front-Cover Texts -.. and no Back-Cover Texts. A copy of the license is included at -.. Documentation/media/uapi/fdl-appendix.rst. -.. -.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections - -.. _control: - -************* -User Controls -************* - -Devices typically have a number of user-settable controls such as -brightness, saturation and so on, which would be presented to the user -on a graphical user interface. But, different devices will have -different controls available, and furthermore, the range of possible -values, and the default value will vary from device to device. The -control ioctls provide the information and a mechanism to create a nice -user interface for these controls that will work correctly with any -device. - -All controls are accessed using an ID value. V4L2 defines several IDs -for specific purposes. Drivers can also implement their own custom -controls using ``V4L2_CID_PRIVATE_BASE`` [#f1]_ and higher values. The -pre-defined control IDs have the prefix ``V4L2_CID_``, and are listed in -:ref:`control-id`. The ID is used when querying the attributes of a -control, and when getting or setting the current value. - -Generally applications should present controls to the user without -assumptions about their purpose. Each control comes with a name string -the user is supposed to understand. When the purpose is non-intuitive -the driver writer should provide a user manual, a user interface plug-in -or a driver specific panel application. Predefined IDs were introduced -to change a few controls programmatically, for example to mute a device -during a channel switch. - -Drivers may enumerate different controls after switching the current -video input or output, tuner or modulator, or audio input or output. -Different in the sense of other bounds, another default and current -value, step size or other menu items. A control with a certain *custom* -ID can also change name and type. - -If a control is not applicable to the current configuration of the -device (for example, it doesn't apply to the current video input) -drivers set the ``V4L2_CTRL_FLAG_INACTIVE`` flag. - -Control values are stored globally, they do not change when switching -except to stay within the reported bounds. They also do not change e. g. -when the device is opened or closed, when the tuner radio frequency is -changed or generally never without application request. - -V4L2 specifies an event mechanism to notify applications when controls -change value (see -:ref:`VIDIOC_SUBSCRIBE_EVENT`, event -``V4L2_EVENT_CTRL``), panel applications might want to make use of that -in order to always reflect the correct control value. - -All controls use machine endianness. - - -.. _control-id: - -Control IDs -=========== - -``V4L2_CID_BASE`` - First predefined ID, equal to ``V4L2_CID_BRIGHTNESS``. - -``V4L2_CID_USER_BASE`` - Synonym of ``V4L2_CID_BASE``. - -``V4L2_CID_BRIGHTNESS`` ``(integer)`` - Picture brightness, or more precisely, the black level. - -``V4L2_CID_CONTRAST`` ``(integer)`` - Picture contrast or luma gain. - -``V4L2_CID_SATURATION`` ``(integer)`` - Picture color saturation or chroma gain. - -``V4L2_CID_HUE`` ``(integer)`` - Hue or color balance. - -``V4L2_CID_AUDIO_VOLUME`` ``(integer)`` - Overall audio volume. Note some drivers also provide an OSS or ALSA - mixer interface. - -``V4L2_CID_AUDIO_BALANCE`` ``(integer)`` - Audio stereo balance. Minimum corresponds to all the way left, - maximum to right. - -``V4L2_CID_AUDIO_BASS`` ``(integer)`` - Audio bass adjustment. - -``V4L2_CID_AUDIO_TREBLE`` ``(integer)`` - Audio treble adjustment. - -``V4L2_CID_AUDIO_MUTE`` ``(boolean)`` - Mute audio, i. e. set the volume to zero, however without affecting - ``V4L2_CID_AUDIO_VOLUME``. Like ALSA drivers, V4L2 drivers must mute - at load time to avoid excessive noise. Actually the entire device - should be reset to a low power consumption state. - -``V4L2_CID_AUDIO_LOUDNESS`` ``(boolean)`` - Loudness mode (bass boost). - -``V4L2_CID_BLACK_LEVEL`` ``(integer)`` - Another name for brightness (not a synonym of - ``V4L2_CID_BRIGHTNESS``). This control is deprecated and should not - be used in new drivers and applications. - -``V4L2_CID_AUTO_WHITE_BALANCE`` ``(boolean)`` - Automatic white balance (cameras). - -``V4L2_CID_DO_WHITE_BALANCE`` ``(button)`` - This is an action control. When set (the value is ignored), the - device will do a white balance and then hold the current setting. - Contrast this with the boolean ``V4L2_CID_AUTO_WHITE_BALANCE``, - which, when activated, keeps adjusting the white balance. - -``V4L2_CID_RED_BALANCE`` ``(integer)`` - Red chroma balance. - -``V4L2_CID_BLUE_BALANCE`` ``(integer)`` - Blue chroma balance. - -``V4L2_CID_GAMMA`` ``(integer)`` - Gamma adjust. - -``V4L2_CID_WHITENESS`` ``(integer)`` - Whiteness for grey-scale devices. This is a synonym for - ``V4L2_CID_GAMMA``. This control is deprecated and should not be - used in new drivers and applications. - -``V4L2_CID_EXPOSURE`` ``(integer)`` - Exposure (cameras). [Unit?] - -``V4L2_CID_AUTOGAIN`` ``(boolean)`` - Automatic gain/exposure control. - -``V4L2_CID_GAIN`` ``(integer)`` - Gain control. - - Primarily used to control gain on e.g. TV tuners but also on - webcams. Most devices control only digital gain with this control - but on some this could include analogue gain as well. Devices that - recognise the difference between digital and analogue gain use - controls ``V4L2_CID_DIGITAL_GAIN`` and ``V4L2_CID_ANALOGUE_GAIN``. - -``V4L2_CID_HFLIP`` ``(boolean)`` - Mirror the picture horizontally. - -``V4L2_CID_VFLIP`` ``(boolean)`` - Mirror the picture vertically. - -.. _v4l2-power-line-frequency: - -``V4L2_CID_POWER_LINE_FREQUENCY`` ``(enum)`` - Enables a power line frequency filter to avoid flicker. Possible - values for ``enum v4l2_power_line_frequency`` are: - ``V4L2_CID_POWER_LINE_FREQUENCY_DISABLED`` (0), - ``V4L2_CID_POWER_LINE_FREQUENCY_50HZ`` (1), - ``V4L2_CID_POWER_LINE_FREQUENCY_60HZ`` (2) and - ``V4L2_CID_POWER_LINE_FREQUENCY_AUTO`` (3). - -``V4L2_CID_HUE_AUTO`` ``(boolean)`` - Enables automatic hue control by the device. The effect of setting - ``V4L2_CID_HUE`` while automatic hue control is enabled is - undefined, drivers should ignore such request. - -``V4L2_CID_WHITE_BALANCE_TEMPERATURE`` ``(integer)`` - This control specifies the white balance settings as a color - temperature in Kelvin. A driver should have a minimum of 2800 - (incandescent) to 6500 (daylight). For more information about color - temperature see - `Wikipedia <http://en.wikipedia.org/wiki/Color_temperature>`__. - -``V4L2_CID_SHARPNESS`` ``(integer)`` - Adjusts the sharpness filters in a camera. The minimum value - disables the filters, higher values give a sharper picture. - -``V4L2_CID_BACKLIGHT_COMPENSATION`` ``(integer)`` - Adjusts the backlight compensation in a camera. The minimum value - disables backlight compensation. - -``V4L2_CID_CHROMA_AGC`` ``(boolean)`` - Chroma automatic gain control. - -``V4L2_CID_CHROMA_GAIN`` ``(integer)`` - Adjusts the Chroma gain control (for use when chroma AGC is - disabled). - -``V4L2_CID_COLOR_KILLER`` ``(boolean)`` - Enable the color killer (i. e. force a black & white image in case - of a weak video signal). - -.. _v4l2-colorfx: - -``V4L2_CID_COLORFX`` ``(enum)`` - Selects a color effect. The following values are defined: - - - -.. tabularcolumns:: |p{5.5cm}|p{12cm}| - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - :widths: 11 24 - - * - ``V4L2_COLORFX_NONE`` - - Color effect is disabled. - * - ``V4L2_COLORFX_ANTIQUE`` - - An aging (old photo) effect. - * - ``V4L2_COLORFX_ART_FREEZE`` - - Frost color effect. - * - ``V4L2_COLORFX_AQUA`` - - Water color, cool tone. - * - ``V4L2_COLORFX_BW`` - - Black and white. - * - ``V4L2_COLORFX_EMBOSS`` - - Emboss, the highlights and shadows replace light/dark boundaries - and low contrast areas are set to a gray background. - * - ``V4L2_COLORFX_GRASS_GREEN`` - - Grass green. - * - ``V4L2_COLORFX_NEGATIVE`` - - Negative. - * - ``V4L2_COLORFX_SEPIA`` - - Sepia tone. - * - ``V4L2_COLORFX_SKETCH`` - - Sketch. - * - ``V4L2_COLORFX_SKIN_WHITEN`` - - Skin whiten. - * - ``V4L2_COLORFX_SKY_BLUE`` - - Sky blue. - * - ``V4L2_COLORFX_SOLARIZATION`` - - Solarization, the image is partially reversed in tone, only color - values above or below a certain threshold are inverted. - * - ``V4L2_COLORFX_SILHOUETTE`` - - Silhouette (outline). - * - ``V4L2_COLORFX_VIVID`` - - Vivid colors. - * - ``V4L2_COLORFX_SET_CBCR`` - - The Cb and Cr chroma components are replaced by fixed coefficients - determined by ``V4L2_CID_COLORFX_CBCR`` control. - - - -``V4L2_CID_COLORFX_CBCR`` ``(integer)`` - Determines the Cb and Cr coefficients for ``V4L2_COLORFX_SET_CBCR`` - color effect. Bits [7:0] of the supplied 32 bit value are - interpreted as Cr component, bits [15:8] as Cb component and bits - [31:16] must be zero. - -``V4L2_CID_AUTOBRIGHTNESS`` ``(boolean)`` - Enable Automatic Brightness. - -``V4L2_CID_ROTATE`` ``(integer)`` - Rotates the image by specified angle. Common angles are 90, 270 and - 180. Rotating the image to 90 and 270 will reverse the height and - width of the display window. It is necessary to set the new height - and width of the picture using the - :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl according to the - rotation angle selected. - -``V4L2_CID_BG_COLOR`` ``(integer)`` - Sets the background color on the current output device. Background - color needs to be specified in the RGB24 format. The supplied 32 bit - value is interpreted as bits 0-7 Red color information, bits 8-15 - Green color information, bits 16-23 Blue color information and bits - 24-31 must be zero. - -``V4L2_CID_ILLUMINATORS_1 V4L2_CID_ILLUMINATORS_2`` ``(boolean)`` - Switch on or off the illuminator 1 or 2 of the device (usually a - microscope). - -``V4L2_CID_MIN_BUFFERS_FOR_CAPTURE`` ``(integer)`` - This is a read-only control that can be read by the application and - used as a hint to determine the number of CAPTURE buffers to pass to - REQBUFS. The value is the minimum number of CAPTURE buffers that is - necessary for hardware to work. - -``V4L2_CID_MIN_BUFFERS_FOR_OUTPUT`` ``(integer)`` - This is a read-only control that can be read by the application and - used as a hint to determine the number of OUTPUT buffers to pass to - REQBUFS. The value is the minimum number of OUTPUT buffers that is - necessary for hardware to work. - -.. _v4l2-alpha-component: - -``V4L2_CID_ALPHA_COMPONENT`` ``(integer)`` - Sets the alpha color component. When a capture device (or capture - queue of a mem-to-mem device) produces a frame format that includes - an alpha component (e.g. - :ref:`packed RGB image formats <pixfmt-rgb>`) and the alpha value - is not defined by the device or the mem-to-mem input data this - control lets you select the alpha component value of all pixels. - When an output device (or output queue of a mem-to-mem device) - consumes a frame format that doesn't include an alpha component and - the device supports alpha channel processing this control lets you - set the alpha component value of all pixels for further processing - in the device. - -``V4L2_CID_LASTP1`` - End of the predefined control IDs (currently - ``V4L2_CID_ALPHA_COMPONENT`` + 1). - -``V4L2_CID_PRIVATE_BASE`` - ID of the first custom (driver specific) control. Applications - depending on particular custom controls should check the driver name - and version, see :ref:`querycap`. - -Applications can enumerate the available controls with the -:ref:`VIDIOC_QUERYCTRL` and -:ref:`VIDIOC_QUERYMENU <VIDIOC_QUERYCTRL>` ioctls, get and set a -control value with the :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and -:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls. Drivers must implement -``VIDIOC_QUERYCTRL``, ``VIDIOC_G_CTRL`` and ``VIDIOC_S_CTRL`` when the -device has one or more controls, ``VIDIOC_QUERYMENU`` when it has one or -more menu type controls. - - -.. _enum_all_controls: - -Example: Enumerating all controls -================================= - -.. code-block:: c - - struct v4l2_queryctrl queryctrl; - struct v4l2_querymenu querymenu; - - static void enumerate_menu(__u32 id) - { - printf(" Menu items:\\n"); - - memset(&querymenu, 0, sizeof(querymenu)); - querymenu.id = id; - - for (querymenu.index = queryctrl.minimum; - querymenu.index <= queryctrl.maximum; - querymenu.index++) { - if (0 == ioctl(fd, VIDIOC_QUERYMENU, &querymenu)) { - printf(" %s\\n", querymenu.name); - } - } - } - - memset(&queryctrl, 0, sizeof(queryctrl)); - - queryctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL; - while (0 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) { - if (!(queryctrl.flags & V4L2_CTRL_FLAG_DISABLED)) { - printf("Control %s\\n", queryctrl.name); - - if (queryctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu(queryctrl.id); - } - - queryctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; - } - if (errno != EINVAL) { - perror("VIDIOC_QUERYCTRL"); - exit(EXIT_FAILURE); - } - -Example: Enumerating all controls including compound controls -============================================================= - -.. code-block:: c - - struct v4l2_query_ext_ctrl query_ext_ctrl; - - memset(&query_ext_ctrl, 0, sizeof(query_ext_ctrl)); - - query_ext_ctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL | V4L2_CTRL_FLAG_NEXT_COMPOUND; - while (0 == ioctl(fd, VIDIOC_QUERY_EXT_CTRL, &query_ext_ctrl)) { - if (!(query_ext_ctrl.flags & V4L2_CTRL_FLAG_DISABLED)) { - printf("Control %s\\n", query_ext_ctrl.name); - - if (query_ext_ctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu(query_ext_ctrl.id); - } - - query_ext_ctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL | V4L2_CTRL_FLAG_NEXT_COMPOUND; - } - if (errno != EINVAL) { - perror("VIDIOC_QUERY_EXT_CTRL"); - exit(EXIT_FAILURE); - } - -Example: Enumerating all user controls (old style) -================================================== - -.. code-block:: c - - - memset(&queryctrl, 0, sizeof(queryctrl)); - - for (queryctrl.id = V4L2_CID_BASE; - queryctrl.id < V4L2_CID_LASTP1; - queryctrl.id++) { - if (0 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) { - if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) - continue; - - printf("Control %s\\n", queryctrl.name); - - if (queryctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu(queryctrl.id); - } else { - if (errno == EINVAL) - continue; - - perror("VIDIOC_QUERYCTRL"); - exit(EXIT_FAILURE); - } - } - - for (queryctrl.id = V4L2_CID_PRIVATE_BASE;; - queryctrl.id++) { - if (0 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) { - if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) - continue; - - printf("Control %s\\n", queryctrl.name); - - if (queryctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu(queryctrl.id); - } else { - if (errno == EINVAL) - break; - - perror("VIDIOC_QUERYCTRL"); - exit(EXIT_FAILURE); - } - } - - -Example: Changing controls -========================== - -.. code-block:: c - - struct v4l2_queryctrl queryctrl; - struct v4l2_control control; - - memset(&queryctrl, 0, sizeof(queryctrl)); - queryctrl.id = V4L2_CID_BRIGHTNESS; - - if (-1 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) { - if (errno != EINVAL) { - perror("VIDIOC_QUERYCTRL"); - exit(EXIT_FAILURE); - } else { - printf("V4L2_CID_BRIGHTNESS is not supportedn"); - } - } else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) { - printf("V4L2_CID_BRIGHTNESS is not supportedn"); - } else { - memset(&control, 0, sizeof (control)); - control.id = V4L2_CID_BRIGHTNESS; - control.value = queryctrl.default_value; - - if (-1 == ioctl(fd, VIDIOC_S_CTRL, &control)) { - perror("VIDIOC_S_CTRL"); - exit(EXIT_FAILURE); - } - } - - memset(&control, 0, sizeof(control)); - control.id = V4L2_CID_CONTRAST; - - if (0 == ioctl(fd, VIDIOC_G_CTRL, &control)) { - control.value += 1; - - /* The driver may clamp the value or return ERANGE, ignored here */ - - if (-1 == ioctl(fd, VIDIOC_S_CTRL, &control) - && errno != ERANGE) { - perror("VIDIOC_S_CTRL"); - exit(EXIT_FAILURE); - } - /* Ignore if V4L2_CID_CONTRAST is unsupported */ - } else if (errno != EINVAL) { - perror("VIDIOC_G_CTRL"); - exit(EXIT_FAILURE); - } - - control.id = V4L2_CID_AUDIO_MUTE; - control.value = 1; /* silence */ - - /* Errors ignored */ - ioctl(fd, VIDIOC_S_CTRL, &control); - -.. [#f1] - The use of ``V4L2_CID_PRIVATE_BASE`` is problematic because different - drivers may use the same ``V4L2_CID_PRIVATE_BASE`` ID for different - controls. This makes it hard to programmatically set such controls - since the meaning of the control with that ID is driver dependent. In - order to resolve this drivers use unique IDs and the - ``V4L2_CID_PRIVATE_BASE`` IDs are mapped to those unique IDs by the - kernel. Consider these ``V4L2_CID_PRIVATE_BASE`` IDs as aliases to - the real IDs. - - Many applications today still use the ``V4L2_CID_PRIVATE_BASE`` IDs - instead of using :ref:`VIDIOC_QUERYCTRL` with - the ``V4L2_CTRL_FLAG_NEXT_CTRL`` flag to enumerate all IDs, so - support for ``V4L2_CID_PRIVATE_BASE`` is still around. |