From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml | 307 +++++++++++++++++++++++ 1 file changed, 307 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml (limited to 'Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml') diff --git a/Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml b/Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml new file mode 100644 index 00000000..3aa7f8f9 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-g-ext-ctrls.xml @@ -0,0 +1,307 @@ + + + ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, +VIDIOC_TRY_EXT_CTRLS + &manvol; + + + + VIDIOC_G_EXT_CTRLS + VIDIOC_S_EXT_CTRLS + VIDIOC_TRY_EXT_CTRLS + Get or set the value of several controls, try control +values + + + + + + int ioctl + int fd + int request + struct v4l2_ext_controls +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, +VIDIOC_TRY_EXT_CTRLS + + + + argp + + + + + + + + + Description + + These ioctls allow the caller to get or set multiple +controls atomically. Control IDs are grouped into control classes (see +) and all controls in the control array +must belong to the same control class. + + Applications must always fill in the +count, +ctrl_class, +controls and +reserved fields of &v4l2-ext-controls;, and +initialize the &v4l2-ext-control; array pointed to by the +controls fields. + + To get the current value of a set of controls applications +initialize the id, +size and reserved2 fields +of each &v4l2-ext-control; and call the +VIDIOC_G_EXT_CTRLS ioctl. String controls controls +must also set the string field. + + If the size is too small to +receive the control result (only relevant for pointer-type controls +like strings), then the driver will set size +to a valid value and return an &ENOSPC;. You should re-allocate the +string memory to this new size and try again. It is possible that the +same issue occurs again if the string has grown in the meantime. It is +recommended to call &VIDIOC-QUERYCTRL; first and use +maximum+1 as the new size +value. It is guaranteed that that is sufficient memory. + + + To change the value of a set of controls applications +initialize the id, size, +reserved2 and +value/string fields of each &v4l2-ext-control; and +call the VIDIOC_S_EXT_CTRLS ioctl. The controls +will only be set if all control values are +valid. + + To check if a set of controls have correct values applications +initialize the id, size, +reserved2 and +value/string fields of each &v4l2-ext-control; and +call the VIDIOC_TRY_EXT_CTRLS ioctl. It is up to +the driver whether wrong values are automatically adjusted to a valid +value or if an error is returned. + + When the id or +ctrl_class is invalid drivers return an +&EINVAL;. When the value is out of bounds drivers can choose to take +the closest valid value or return an &ERANGE;, whatever seems more +appropriate. In the first case the new value is set in +&v4l2-ext-control;. + + 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 (⪚ a failed i2c +command) can still cause this situation. + + + struct <structname>v4l2_ext_control</structname> + + &cs-ustr; + + + __u32 + id + + 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 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. Note that for string controls +this size field should not be confused with the length of the string. +This field refers to the size of the memory that contains the string. +The actual length of the string may well be much smaller. + + + + __u32 + reserved2[1] + + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + union + (anonymous) + + + + __s32 + value + New value or current value. + + + + __s64 + value64 + New value or current value. + + + + char * + string + A pointer to a string. + + + +
+ + + struct <structname>v4l2_ext_controls</structname> + + &cs-str; + + + __u32 + ctrl_class + The control class to which all controls belong, see +. + + + __u32 + count + The number of controls in the controls array. May +also be zero. + + + __u32 + error_idx + Set by the driver in case of an error. It is the +index of the control causing the error or equal to 'count' when the +error is not associated with a particular control. Undefined when the +ioctl returns 0 (success). + + + __u32 + reserved[2] + Reserved for future extensions. Drivers and +applications must set the array to zero. + + + &v4l2-ext-control; * + controls + Pointer to an array of +count v4l2_ext_control structures. Ignored +if count equals zero. + + + +
+ + + Control classes + + &cs-def; + + + V4L2_CTRL_CLASS_USER + 0x980000 + The class containing user controls. These controls +are described in . All controls that can be set +using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this +class. + + + V4L2_CTRL_CLASS_MPEG + 0x990000 + The class containing MPEG compression controls. +These controls are described in . + + + V4L2_CTRL_CLASS_CAMERA + 0x9a0000 + The class containing camera controls. +These controls are described in . + + + V4L2_CTRL_CLASS_FM_TX + 0x9b0000 + The class containing FM Transmitter (FM TX) controls. +These controls are described in . + + + +
+ + + + + &return-value; + + + + EINVAL + + The &v4l2-ext-control; id +is invalid or the &v4l2-ext-controls; +ctrl_class is invalid. This error code is +also returned by the VIDIOC_S_EXT_CTRLS and +VIDIOC_TRY_EXT_CTRLS ioctls if two or more +control values are in conflict. + + + + ERANGE + + The &v4l2-ext-control; value +is out of bounds. + + + + EBUSY + + The control is temporarily not changeable, possibly +because another applications took over control of the device function +this control belongs to. + + + + ENOSPC + + The space reserved for the control's payload is insufficient. +The field size is set to a value that is enough +to store the payload and this error code is returned. + + + + + + + -- cgit v1.2.3