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-queryctrl.xml | 434 +++++++++++++++++++++++++ 1 file changed, 434 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-queryctrl.xml (limited to 'Documentation/DocBook/v4l/vidioc-queryctrl.xml') diff --git a/Documentation/DocBook/v4l/vidioc-queryctrl.xml b/Documentation/DocBook/v4l/vidioc-queryctrl.xml new file mode 100644 index 00000000..0d5e8283 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-queryctrl.xml @@ -0,0 +1,434 @@ + + + ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU + &manvol; + + + + VIDIOC_QUERYCTRL + VIDIOC_QUERYMENU + Enumerate controls and menu control items + + + + + + int ioctl + int fd + int request + struct v4l2_queryctrl *argp + + + + + int ioctl + int fd + int request + struct v4l2_querymenu *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU + + + + argp + + + + + + + + + Description + + To query the attributes of a control applications set the +id field of a &v4l2-queryctrl; and call the +VIDIOC_QUERYCTRL ioctl with a pointer to this +structure. The driver fills the rest of the structure or returns an +&EINVAL; when the id is invalid. + + It is possible to enumerate controls by calling +VIDIOC_QUERYCTRL with successive +id values starting from +V4L2_CID_BASE up to and exclusive +V4L2_CID_BASE_LASTP1. Drivers may return +EINVAL if a control in this range is not +supported. Further applications can enumerate private controls, which +are not defined in this specification, by starting at +V4L2_CID_PRIVATE_BASE and incrementing +id until the driver returns +EINVAL. + + In both cases, when the driver sets the +V4L2_CTRL_FLAG_DISABLED flag in the +flags field this control is permanently +disabled and should be ignored by the application. + V4L2_CTRL_FLAG_DISABLED was +intended for two purposes: Drivers can skip predefined controls not +supported by the hardware (although returning EINVAL would do as +well), or disable predefined and private controls after hardware +detection without the trouble of reordering control arrays and indices +(EINVAL cannot be used to skip private controls because it would +prematurely end the enumeration). + + When the application ORs id with +V4L2_CTRL_FLAG_NEXT_CTRL the driver returns the +next supported control, or EINVAL if there is +none. Drivers which do not support this flag yet always return +EINVAL. + + Additional information is required for menu controls: the +names of the menu items. To query them applications set the +id and index +fields of &v4l2-querymenu; and call the +VIDIOC_QUERYMENU ioctl with a pointer to this +structure. The driver fills the rest of the structure or returns an +&EINVAL; when the id or +index is invalid. Menu items are enumerated +by calling VIDIOC_QUERYMENU with successive +index values from &v4l2-queryctrl; +minimum to +maximum, inclusive. Note that it is possible +for VIDIOC_QUERYMENU to return an &EINVAL; for some +indices between minimum and maximum. +In that case that particular menu item is not supported by this driver. Also note that +the minimum value is not necessarily 0. + + See also the examples in . + + + struct <structname>v4l2_queryctrl</structname> + + &cs-str; + + + __u32 + id + Identifies the control, set by the application. See + 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;. + + + &v4l2-ctrl-type; + type + Type of control, see . + + + __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 V4L2_CTRL_TYPE_INTEGER controls and the +lowest valid index for V4L2_CTRL_TYPE_MENU controls. +For V4L2_CTRL_TYPE_STRING controls the minimum value +gives the minimum length of the string. This length does not include the terminating +zero. It may not be valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 controls. Note that this is a +signed value. + + + __s32 + maximum + Maximum value, inclusive. This field gives an upper +bound for V4L2_CTRL_TYPE_INTEGER controls and the +highest valid index for V4L2_CTRL_TYPE_MENU +controls. +For V4L2_CTRL_TYPE_STRING controls the maximum value +gives the maximum length of the string. This length does not include the terminating +zero. It may not be valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 controls. Note that this is a +signed value. + + + __s32 + step + This field gives a step size for +V4L2_CTRL_TYPE_INTEGER controls. For +V4L2_CTRL_TYPE_STRING controls this field refers to +the string length that has to be a multiple of this step size. +It may not be valid for any other type of control, including +V4L2_CTRL_TYPE_INTEGER64 +controls.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 or _MENU control. +Not valid for other types of controls. Drivers reset controls only +when the driver is loaded, not later, in particular not when the +func-open; is called. + + + __u32 + flags + Control flags, see . + + + __u32 + reserved[2] + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + struct <structname>v4l2_querymenu</structname> + + &cs-str; + + + __u32 + id + Identifies the control, set by the application +from the respective &v4l2-queryctrl; +id. + + + __u32 + index + Index of the menu item, starting at zero, set by + the application. + + + __u8 + name[32] + Name of the menu item, a NUL-terminated ASCII +string. This information is intended for the user. + + + __u32 + reserved + Reserved for future extensions. Drivers must set +the array to zero. + + + +
+ + + enum v4l2_ctrl_type + + + + + + + + + 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 which are actually different on the hardware. + + + 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_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; on a +VIDIOC_G_CTRL attempt. + + + V4L2_CTRL_TYPE_INTEGER64 + n/a + n/a + n/a + A 64-bit integer valued control. Minimum, maximum +and step size cannot be queried. + + + 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 &VIDIOC-S-EXT-CTRLS; you need to set the +size field of &v4l2-ext-control; to 9. For &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 ) + 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;. + + + +
+ + + Control Flags + + &cs-def; + + + 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;. + + + 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;. + + + V4L2_CTRL_FLAG_READ_ONLY + 0x0004 + This control is permanently readable only. Any +attempt to change the control will result in an &EINVAL;. + + + 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. 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 +(⪚ motor control) but no meaningful value can be returned. + + + +
+ + + + &return-value; + + + + EINVAL + + The &v4l2-queryctrl; id +is invalid. The &v4l2-querymenu; id is +invalid or index is out of range (less than +minimum or greater than maximum) +or this particular menu item is not supported by the driver. + + + + EACCES + + An attempt was made to read a write-only control. + + + + + + + -- cgit v1.2.3