diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst | 59 |
1 files changed, 49 insertions, 10 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst b/Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst index 2011c2b2ee675..d9930fe776cf8 100644 --- a/Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst +++ b/Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst @@ -95,6 +95,25 @@ appropriate. In the first case the new value is set in struct is inappropriate (e.g. the given menu index is not supported by the menu control), then this will also result in an ``EINVAL`` error code error. +If ``request_fd`` is set to a not-yet-queued :ref:`request <media-request-api>` +file descriptor and ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``, +then the controls are not applied immediately when calling +:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, but instead are applied by +the driver for the buffer associated with the same request. +If the device does not support requests, then ``EACCES`` will be returned. +If requests are supported but an invalid request file descriptor is given, +then ``EINVAL`` will be returned. + +An attempt to call :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` for a +request that has already been queued will result in an ``EBUSY`` error. + +If ``request_fd`` is specified and ``which`` is set to +``V4L2_CTRL_WHICH_REQUEST_VAL`` during a call to +:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, then it will return the +values of the controls at the time of request completion. +If the request is not yet completed, then this will result in an +``EACCES`` error. + The driver will only set/get these controls if all control values are correct. This prevents the situation where only some of the controls were set/get. Only low-level errors (e. g. a failed i2c command) can @@ -209,13 +228,17 @@ still cause this situation. - ``which`` - Which value of the control to get/set/try. ``V4L2_CTRL_WHICH_CUR_VAL`` will return the current value of the - control and ``V4L2_CTRL_WHICH_DEF_VAL`` will return the default - value of the control. + 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:: - 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 @@ -272,8 +295,15 @@ still cause this situation. then you can call :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` to try to discover the actual control that failed the validation step. Unfortunately, there is no ``TRY`` equivalent for :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`. + * - __s32 + - ``request_fd`` + - File descriptor of the request to be used by this operation. Only + valid if ``which`` is set to ``V4L2_CTRL_WHICH_REQUEST_VAL``. + If the device does not support requests, then ``EACCES`` will be returned. + If requests are supported but an invalid request file descriptor is + given, then ``EINVAL`` will be returned. * - __u32 - - ``reserved``\ [2] + - ``reserved``\ [1] - Reserved for future extensions. Drivers and applications must set the array to zero. @@ -347,11 +377,14 @@ appropriately. The generic error codes are described at the EINVAL The struct :c:type:`v4l2_ext_control` ``id`` is - invalid, the struct :c:type:`v4l2_ext_controls` + invalid, or the struct :c:type:`v4l2_ext_controls` ``which`` is invalid, or the struct :c:type:`v4l2_ext_control` ``value`` was inappropriate (e.g. the given menu index is not supported by the - driver). This error code is also returned by the + driver), or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` + but the given ``request_fd`` was invalid or ``V4L2_CTRL_WHICH_REQUEST_VAL`` + is not supported by the kernel. + This error code is also returned by the :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls if two or more control values are in conflict. @@ -362,7 +395,9 @@ ERANGE EBUSY The control is temporarily not changeable, possibly because another applications took over control of the device function this control - belongs to. + belongs to, or (if the ``which`` field was set to + ``V4L2_CTRL_WHICH_REQUEST_VAL``) the request was queued but not yet + completed. ENOSPC The space reserved for the control's payload is insufficient. The @@ -370,5 +405,9 @@ ENOSPC and this error code is returned. EACCES - Attempt to try or set a read-only control or to get a write-only - control. + Attempt to try or set a read-only control, or to get a write-only + control, or to get a control from a request that has not yet been + completed. + + Or the ``which`` field was set to ``V4L2_CTRL_WHICH_REQUEST_VAL`` but the + device does not support requests. |