diff options
Diffstat (limited to 'Documentation/video4linux/v4l2-controls.txt')
| -rw-r--r-- | Documentation/video4linux/v4l2-controls.txt | 57 |
1 files changed, 46 insertions, 11 deletions
diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt index 43da22b8972..06cf3ac8363 100644 --- a/Documentation/video4linux/v4l2-controls.txt +++ b/Documentation/video4linux/v4l2-controls.txt @@ -124,13 +124,22 @@ You add non-menu controls by calling v4l2_ctrl_new_std: const struct v4l2_ctrl_ops *ops, u32 id, s32 min, s32 max, u32 step, s32 def); -Menu controls are added by calling v4l2_ctrl_new_std_menu: +Menu and integer menu controls are added by calling v4l2_ctrl_new_std_menu: struct v4l2_ctrl *v4l2_ctrl_new_std_menu(struct v4l2_ctrl_handler *hdl, const struct v4l2_ctrl_ops *ops, u32 id, s32 max, s32 skip_mask, s32 def); -Or alternatively for integer menu controls, by calling v4l2_ctrl_new_int_menu: +Menu controls with a driver specific menu are added by calling +v4l2_ctrl_new_std_menu_items: + + struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items( + struct v4l2_ctrl_handler *hdl, + const struct v4l2_ctrl_ops *ops, u32 id, s32 max, + s32 skip_mask, s32 def, const char * const *qmenu); + +Integer menu controls with a driver specific menu can be added by calling +v4l2_ctrl_new_int_menu: struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl, const struct v4l2_ctrl_ops *ops, @@ -141,6 +150,12 @@ These functions are typically called right after the v4l2_ctrl_handler_init: static const s64 exp_bias_qmenu[] = { -2, -1, 0, 1, 2 }; + static const char * const test_pattern[] = { + "Disabled", + "Vertical Bars", + "Solid Black", + "Solid White", + }; v4l2_ctrl_handler_init(&foo->ctrl_handler, nr_of_controls); v4l2_ctrl_new_std(&foo->ctrl_handler, &foo_ctrl_ops, @@ -156,6 +171,9 @@ These functions are typically called right after the v4l2_ctrl_handler_init: ARRAY_SIZE(exp_bias_qmenu) - 1, ARRAY_SIZE(exp_bias_qmenu) / 2 - 1, exp_bias_qmenu); + v4l2_ctrl_new_std_menu_items(&foo->ctrl_handler, &foo_ctrl_ops, + V4L2_CID_TEST_PATTERN, ARRAY_SIZE(test_pattern) - 1, 0, + 0, test_pattern); ... if (foo->ctrl_handler.error) { int err = foo->ctrl_handler.error; @@ -185,6 +203,13 @@ v4l2_ctrl_new_std_menu in that it doesn't have the mask argument and takes as the last argument an array of signed 64-bit integers that form an exact menu item list. +The v4l2_ctrl_new_std_menu_items function is very similar to +v4l2_ctrl_new_std_menu but takes an extra parameter qmenu, which is the driver +specific menu for an otherwise standard menu control. A good example for this +control is the test pattern control for capture/display/sensors devices that +have the capability to generate test patterns. These test patterns are hardware +specific, so the contents of the menu will vary from device to device. + Note that if something fails, the function will return NULL or an error and set ctrl_handler->error to the error code. If ctrl_handler->error was already set, then it will just return and do nothing. This is also true for @@ -594,7 +619,11 @@ handler and finally add the first handler to the second. For example: v4l2_ctrl_new_std(&radio_ctrl_handler, &radio_ops, V4L2_CID_AUDIO_MUTE, ...); v4l2_ctrl_new_std(&video_ctrl_handler, &video_ops, V4L2_CID_BRIGHTNESS, ...); v4l2_ctrl_new_std(&video_ctrl_handler, &video_ops, V4L2_CID_CONTRAST, ...); - v4l2_ctrl_add_handler(&video_ctrl_handler, &radio_ctrl_handler); + v4l2_ctrl_add_handler(&video_ctrl_handler, &radio_ctrl_handler, NULL); + +The last argument to v4l2_ctrl_add_handler() is a filter function that allows +you to filter which controls will be added. Set it to NULL if you want to add +all controls. Or you can add specific controls to a handler: @@ -687,14 +716,20 @@ a control of this type whenever the first control belonging to a new control class is added. -Proposals for Extensions -======================== +Adding Notify Callbacks +======================= + +Sometimes the platform or bridge driver needs to be notified when a control +from a sub-device driver changes. You can set a notify callback by calling +this function: -Some ideas for future extensions to the spec: +void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl, + void (*notify)(struct v4l2_ctrl *ctrl, void *priv), void *priv); -1) Add a V4L2_CTRL_FLAG_HEX to have values shown as hexadecimal instead of -decimal. Useful for e.g. video_mute_yuv. +Whenever the give control changes value the notify callback will be called +with a pointer to the control and the priv pointer that was passed with +v4l2_ctrl_notify. Note that the control's handler lock is held when the +notify function is called. -2) It is possible to mark in the controls array which controls have been -successfully written and which failed by for example adding a bit to the -control ID. Not sure if it is worth the effort, though. +There can be only one notify function per control handler. Any attempt +to set another notify function will cause a WARN_ON. |