--- /dev/null
- And set all core control ops in your struct v4l2_subdev_core_ops to these
- helpers:
-
- .. code-block:: none
-
- .queryctrl = v4l2_subdev_queryctrl,
- .querymenu = v4l2_subdev_querymenu,
- .g_ctrl = v4l2_subdev_g_ctrl,
- .s_ctrl = v4l2_subdev_s_ctrl,
- .g_ext_ctrls = v4l2_subdev_g_ext_ctrls,
- .try_ext_ctrls = v4l2_subdev_try_ext_ctrls,
- .s_ext_ctrls = v4l2_subdev_s_ext_ctrls,
-
- Note: this is a temporary solution only. Once all V4L2 drivers that depend
- on subdev drivers are converted to the control framework these helpers will
- no longer be needed.
-
+V4L2 Controls
+=============
+
+Introduction
+------------
+
+The V4L2 control API seems simple enough, but quickly becomes very hard to
+implement correctly in drivers. But much of the code needed to handle controls
+is actually not driver specific and can be moved to the V4L core framework.
+
+After all, the only part that a driver developer is interested in is:
+
+1) How do I add a control?
+2) How do I set the control's value? (i.e. s_ctrl)
+
+And occasionally:
+
+3) How do I get the control's value? (i.e. g_volatile_ctrl)
+4) How do I validate the user's proposed control value? (i.e. try_ctrl)
+
+All the rest is something that can be done centrally.
+
+The control framework was created in order to implement all the rules of the
+V4L2 specification with respect to controls in a central place. And to make
+life as easy as possible for the driver developer.
+
+Note that the control framework relies on the presence of a struct v4l2_device
+for V4L2 drivers and struct v4l2_subdev for sub-device drivers.
+
+
+Objects in the framework
+------------------------
+
+There are two main objects:
+
+The v4l2_ctrl object describes the control properties and keeps track of the
+control's value (both the current value and the proposed new value).
+
+v4l2_ctrl_handler is the object that keeps track of controls. It maintains a
+list of v4l2_ctrl objects that it owns and another list of references to
+controls, possibly to controls owned by other handlers.
+
+
+Basic usage for V4L2 and sub-device drivers
+-------------------------------------------
+
+1) Prepare the driver:
+
+1.1) Add the handler to your driver's top-level struct:
+
+.. code-block:: none
+
+ struct foo_dev {
+ ...
+ struct v4l2_ctrl_handler ctrl_handler;
+ ...
+ };
+
+ struct foo_dev *foo;
+
+1.2) Initialize the handler:
+
+.. code-block:: none
+
+ v4l2_ctrl_handler_init(&foo->ctrl_handler, nr_of_controls);
+
+The second argument is a hint telling the function how many controls this
+handler is expected to handle. It will allocate a hashtable based on this
+information. It is a hint only.
+
+1.3) Hook the control handler into the driver:
+
+1.3.1) For V4L2 drivers do this:
+
+.. code-block:: none
+
+ struct foo_dev {
+ ...
+ struct v4l2_device v4l2_dev;
+ ...
+ struct v4l2_ctrl_handler ctrl_handler;
+ ...
+ };
+
+ foo->v4l2_dev.ctrl_handler = &foo->ctrl_handler;
+
+Where foo->v4l2_dev is of type struct v4l2_device.
+
+Finally, remove all control functions from your v4l2_ioctl_ops (if any):
+vidioc_queryctrl, vidioc_query_ext_ctrl, vidioc_querymenu, vidioc_g_ctrl,
+vidioc_s_ctrl, vidioc_g_ext_ctrls, vidioc_try_ext_ctrls and vidioc_s_ext_ctrls.
+Those are now no longer needed.
+
+1.3.2) For sub-device drivers do this:
+
+.. code-block:: none
+
+ struct foo_dev {
+ ...
+ struct v4l2_subdev sd;
+ ...
+ struct v4l2_ctrl_handler ctrl_handler;
+ ...
+ };
+
+ foo->sd.ctrl_handler = &foo->ctrl_handler;
+
+Where foo->sd is of type struct v4l2_subdev.
+
+1.4) Clean up the handler at the end:
+
+.. code-block:: none
+
+ v4l2_ctrl_handler_free(&foo->ctrl_handler);
+
+
+2) Add controls:
+
+You add non-menu controls by calling v4l2_ctrl_new_std:
+
+.. code-block:: none
+
+ struct v4l2_ctrl *v4l2_ctrl_new_std(struct v4l2_ctrl_handler *hdl,
+ const struct v4l2_ctrl_ops *ops,
+ u32 id, s32 min, s32 max, u32 step, s32 def);
+
+Menu and integer menu controls are added by calling v4l2_ctrl_new_std_menu:
+
+.. code-block:: none
+
+ 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);
+
+Menu controls with a driver specific menu are added by calling
+v4l2_ctrl_new_std_menu_items:
+
+.. code-block:: none
+
+ 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:
+
+.. code-block:: none
+
+ struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
+ const struct v4l2_ctrl_ops *ops,
+ u32 id, s32 max, s32 def, const s64 *qmenu_int);
+
+These functions are typically called right after the v4l2_ctrl_handler_init:
+
+.. code-block:: none
+
+ 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,
+ V4L2_CID_BRIGHTNESS, 0, 255, 1, 128);
+ v4l2_ctrl_new_std(&foo->ctrl_handler, &foo_ctrl_ops,
+ V4L2_CID_CONTRAST, 0, 255, 1, 128);
+ v4l2_ctrl_new_std_menu(&foo->ctrl_handler, &foo_ctrl_ops,
+ V4L2_CID_POWER_LINE_FREQUENCY,
+ V4L2_CID_POWER_LINE_FREQUENCY_60HZ, 0,
+ V4L2_CID_POWER_LINE_FREQUENCY_DISABLED);
+ v4l2_ctrl_new_int_menu(&foo->ctrl_handler, &foo_ctrl_ops,
+ V4L2_CID_EXPOSURE_BIAS,
+ 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;
+
+ v4l2_ctrl_handler_free(&foo->ctrl_handler);
+ return err;
+ }
+
+The v4l2_ctrl_new_std function returns the v4l2_ctrl pointer to the new
+control, but if you do not need to access the pointer outside the control ops,
+then there is no need to store it.
+
+The v4l2_ctrl_new_std function will fill in most fields based on the control
+ID except for the min, max, step and default values. These are passed in the
+last four arguments. These values are driver specific while control attributes
+like type, name, flags are all global. The control's current value will be set
+to the default value.
+
+The v4l2_ctrl_new_std_menu function is very similar but it is used for menu
+controls. There is no min argument since that is always 0 for menu controls,
+and instead of a step there is a skip_mask argument: if bit X is 1, then menu
+item X is skipped.
+
+The v4l2_ctrl_new_int_menu function creates a new standard integer menu
+control with driver-specific items in the menu. It differs from
+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
+v4l2_ctrl_handler_init if it cannot allocate the internal data structure.
+
+This makes it easy to init the handler and just add all controls and only check
+the error code at the end. Saves a lot of repetitive error checking.
+
+It is recommended to add controls in ascending control ID order: it will be
+a bit faster that way.
+
+3) Optionally force initial control setup:
+
+.. code-block:: none
+
+ v4l2_ctrl_handler_setup(&foo->ctrl_handler);
+
+This will call s_ctrl for all controls unconditionally. Effectively this
+initializes the hardware to the default control values. It is recommended
+that you do this as this ensures that both the internal data structures and
+the hardware are in sync.
+
+4) Finally: implement the v4l2_ctrl_ops
+
+.. code-block:: none
+
+ static const struct v4l2_ctrl_ops foo_ctrl_ops = {
+ .s_ctrl = foo_s_ctrl,
+ };
+
+Usually all you need is s_ctrl:
+
+.. code-block:: none
+
+ static int foo_s_ctrl(struct v4l2_ctrl *ctrl)
+ {
+ struct foo *state = container_of(ctrl->handler, struct foo, ctrl_handler);
+
+ switch (ctrl->id) {
+ case V4L2_CID_BRIGHTNESS:
+ write_reg(0x123, ctrl->val);
+ break;
+ case V4L2_CID_CONTRAST:
+ write_reg(0x456, ctrl->val);
+ break;
+ }
+ return 0;
+ }
+
+The control ops are called with the v4l2_ctrl pointer as argument.
+The new control value has already been validated, so all you need to do is
+to actually update the hardware registers.
+
+You're done! And this is sufficient for most of the drivers we have. No need
+to do any validation of control values, or implement QUERYCTRL, QUERY_EXT_CTRL
+and QUERYMENU. And G/S_CTRL as well as G/TRY/S_EXT_CTRLS are automatically supported.
+
+
+.. note::
+
+ The remainder sections deal with more advanced controls topics and scenarios.
+ In practice the basic usage as described above is sufficient for most drivers.
+
+
+Inheriting Controls
+-------------------
+
+When a sub-device is registered with a V4L2 driver by calling
+v4l2_device_register_subdev() and the ctrl_handler fields of both v4l2_subdev
+and v4l2_device are set, then the controls of the subdev will become
+automatically available in the V4L2 driver as well. If the subdev driver
+contains controls that already exist in the V4L2 driver, then those will be
+skipped (so a V4L2 driver can always override a subdev control).
+
+What happens here is that v4l2_device_register_subdev() calls
+v4l2_ctrl_add_handler() adding the controls of the subdev to the controls
+of v4l2_device.
+
+
+Accessing Control Values
+------------------------
+
+The following union is used inside the control framework to access control
+values:
+
+.. code-block:: none
+
+ union v4l2_ctrl_ptr {
+ s32 *p_s32;
+ s64 *p_s64;
+ char *p_char;
+ void *p;
+ };
+
+The v4l2_ctrl struct contains these fields that can be used to access both
+current and new values:
+
+.. code-block:: none
+
+ s32 val;
+ struct {
+ s32 val;
+ } cur;
+
+
+ union v4l2_ctrl_ptr p_new;
+ union v4l2_ctrl_ptr p_cur;
+
+If the control has a simple s32 type type, then:
+
+.. code-block:: none
+
+ &ctrl->val == ctrl->p_new.p_s32
+ &ctrl->cur.val == ctrl->p_cur.p_s32
+
+For all other types use ctrl->p_cur.p<something>. Basically the val
+and cur.val fields can be considered an alias since these are used so often.
+
+Within the control ops you can freely use these. The val and cur.val speak for
+themselves. The p_char pointers point to character buffers of length
+ctrl->maximum + 1, and are always 0-terminated.
+
+Unless the control is marked volatile the p_cur field points to the the
+current cached control value. When you create a new control this value is made
+identical to the default value. After calling v4l2_ctrl_handler_setup() this
+value is passed to the hardware. It is generally a good idea to call this
+function.
+
+Whenever a new value is set that new value is automatically cached. This means
+that most drivers do not need to implement the g_volatile_ctrl() op. The
+exception is for controls that return a volatile register such as a signal
+strength read-out that changes continuously. In that case you will need to
+implement g_volatile_ctrl like this:
+
+.. code-block:: none
+
+ static int foo_g_volatile_ctrl(struct v4l2_ctrl *ctrl)
+ {
+ switch (ctrl->id) {
+ case V4L2_CID_BRIGHTNESS:
+ ctrl->val = read_reg(0x123);
+ break;
+ }
+ }
+
+Note that you use the 'new value' union as well in g_volatile_ctrl. In general
+controls that need to implement g_volatile_ctrl are read-only controls. If they
+are not, a V4L2_EVENT_CTRL_CH_VALUE will not be generated when the control
+changes.
+
+To mark a control as volatile you have to set V4L2_CTRL_FLAG_VOLATILE:
+
+.. code-block:: none
+
+ ctrl = v4l2_ctrl_new_std(&sd->ctrl_handler, ...);
+ if (ctrl)
+ ctrl->flags |= V4L2_CTRL_FLAG_VOLATILE;
+
+For try/s_ctrl the new values (i.e. as passed by the user) are filled in and
+you can modify them in try_ctrl or set them in s_ctrl. The 'cur' union
+contains the current value, which you can use (but not change!) as well.
+
+If s_ctrl returns 0 (OK), then the control framework will copy the new final
+values to the 'cur' union.
+
+While in g_volatile/s/try_ctrl you can access the value of all controls owned
+by the same handler since the handler's lock is held. If you need to access
+the value of controls owned by other handlers, then you have to be very careful
+not to introduce deadlocks.
+
+Outside of the control ops you have to go through to helper functions to get
+or set a single control value safely in your driver:
+
+.. code-block:: none
+
+ s32 v4l2_ctrl_g_ctrl(struct v4l2_ctrl *ctrl);
+ int v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val);
+
+These functions go through the control framework just as VIDIOC_G/S_CTRL ioctls
+do. Don't use these inside the control ops g_volatile/s/try_ctrl, though, that
+will result in a deadlock since these helpers lock the handler as well.
+
+You can also take the handler lock yourself:
+
+.. code-block:: none
+
+ mutex_lock(&state->ctrl_handler.lock);
+ pr_info("String value is '%s'\n", ctrl1->p_cur.p_char);
+ pr_info("Integer value is '%s'\n", ctrl2->cur.val);
+ mutex_unlock(&state->ctrl_handler.lock);
+
+
+Menu Controls
+-------------
+
+The v4l2_ctrl struct contains this union:
+
+.. code-block:: none
+
+ union {
+ u32 step;
+ u32 menu_skip_mask;
+ };
+
+For menu controls menu_skip_mask is used. What it does is that it allows you
+to easily exclude certain menu items. This is used in the VIDIOC_QUERYMENU
+implementation where you can return -EINVAL if a certain menu item is not
+present. Note that VIDIOC_QUERYCTRL always returns a step value of 1 for
+menu controls.
+
+A good example is the MPEG Audio Layer II Bitrate menu control where the
+menu is a list of standardized possible bitrates. But in practice hardware
+implementations will only support a subset of those. By setting the skip
+mask you can tell the framework which menu items should be skipped. Setting
+it to 0 means that all menu items are supported.
+
+You set this mask either through the v4l2_ctrl_config struct for a custom
+control, or by calling v4l2_ctrl_new_std_menu().
+
+
+Custom Controls
+---------------
+
+Driver specific controls can be created using v4l2_ctrl_new_custom():
+
+.. code-block:: none
+
+ static const struct v4l2_ctrl_config ctrl_filter = {
+ .ops = &ctrl_custom_ops,
+ .id = V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER,
+ .name = "Spatial Filter",
+ .type = V4L2_CTRL_TYPE_INTEGER,
+ .flags = V4L2_CTRL_FLAG_SLIDER,
+ .max = 15,
+ .step = 1,
+ };
+
+ ctrl = v4l2_ctrl_new_custom(&foo->ctrl_handler, &ctrl_filter, NULL);
+
+The last argument is the priv pointer which can be set to driver-specific
+private data.
+
+The v4l2_ctrl_config struct also has a field to set the is_private flag.
+
+If the name field is not set, then the framework will assume this is a standard
+control and will fill in the name, type and flags fields accordingly.
+
+
+Active and Grabbed Controls
+---------------------------
+
+If you get more complex relationships between controls, then you may have to
+activate and deactivate controls. For example, if the Chroma AGC control is
+on, then the Chroma Gain control is inactive. That is, you may set it, but
+the value will not be used by the hardware as long as the automatic gain
+control is on. Typically user interfaces can disable such input fields.
+
+You can set the 'active' status using v4l2_ctrl_activate(). By default all
+controls are active. Note that the framework does not check for this flag.
+It is meant purely for GUIs. The function is typically called from within
+s_ctrl.
+
+The other flag is the 'grabbed' flag. A grabbed control means that you cannot
+change it because it is in use by some resource. Typical examples are MPEG
+bitrate controls that cannot be changed while capturing is in progress.
+
+If a control is set to 'grabbed' using v4l2_ctrl_grab(), then the framework
+will return -EBUSY if an attempt is made to set this control. The
+v4l2_ctrl_grab() function is typically called from the driver when it
+starts or stops streaming.
+
+
+Control Clusters
+----------------
+
+By default all controls are independent from the others. But in more
+complex scenarios you can get dependencies from one control to another.
+In that case you need to 'cluster' them:
+
+.. code-block:: none
+
+ struct foo {
+ struct v4l2_ctrl_handler ctrl_handler;
+ #define AUDIO_CL_VOLUME (0)
+ #define AUDIO_CL_MUTE (1)
+ struct v4l2_ctrl *audio_cluster[2];
+ ...
+ };
+
+ state->audio_cluster[AUDIO_CL_VOLUME] =
+ v4l2_ctrl_new_std(&state->ctrl_handler, ...);
+ state->audio_cluster[AUDIO_CL_MUTE] =
+ v4l2_ctrl_new_std(&state->ctrl_handler, ...);
+ v4l2_ctrl_cluster(ARRAY_SIZE(state->audio_cluster), state->audio_cluster);
+
+From now on whenever one or more of the controls belonging to the same
+cluster is set (or 'gotten', or 'tried'), only the control ops of the first
+control ('volume' in this example) is called. You effectively create a new
+composite control. Similar to how a 'struct' works in C.
+
+So when s_ctrl is called with V4L2_CID_AUDIO_VOLUME as argument, you should set
+all two controls belonging to the audio_cluster:
+
+.. code-block:: none
+
+ static int foo_s_ctrl(struct v4l2_ctrl *ctrl)
+ {
+ struct foo *state = container_of(ctrl->handler, struct foo, ctrl_handler);
+
+ switch (ctrl->id) {
+ case V4L2_CID_AUDIO_VOLUME: {
+ struct v4l2_ctrl *mute = ctrl->cluster[AUDIO_CL_MUTE];
+
+ write_reg(0x123, mute->val ? 0 : ctrl->val);
+ break;
+ }
+ case V4L2_CID_CONTRAST:
+ write_reg(0x456, ctrl->val);
+ break;
+ }
+ return 0;
+ }
+
+In the example above the following are equivalent for the VOLUME case:
+
+.. code-block:: none
+
+ ctrl == ctrl->cluster[AUDIO_CL_VOLUME] == state->audio_cluster[AUDIO_CL_VOLUME]
+ ctrl->cluster[AUDIO_CL_MUTE] == state->audio_cluster[AUDIO_CL_MUTE]
+
+In practice using cluster arrays like this becomes very tiresome. So instead
+the following equivalent method is used:
+
+.. code-block:: none
+
+ struct {
+ /* audio cluster */
+ struct v4l2_ctrl *volume;
+ struct v4l2_ctrl *mute;
+ };
+
+The anonymous struct is used to clearly 'cluster' these two control pointers,
+but it serves no other purpose. The effect is the same as creating an
+array with two control pointers. So you can just do:
+
+.. code-block:: none
+
+ state->volume = v4l2_ctrl_new_std(&state->ctrl_handler, ...);
+ state->mute = v4l2_ctrl_new_std(&state->ctrl_handler, ...);
+ v4l2_ctrl_cluster(2, &state->volume);
+
+And in foo_s_ctrl you can use these pointers directly: state->mute->val.
+
+Note that controls in a cluster may be NULL. For example, if for some
+reason mute was never added (because the hardware doesn't support that
+particular feature), then mute will be NULL. So in that case we have a
+cluster of 2 controls, of which only 1 is actually instantiated. The
+only restriction is that the first control of the cluster must always be
+present, since that is the 'master' control of the cluster. The master
+control is the one that identifies the cluster and that provides the
+pointer to the v4l2_ctrl_ops struct that is used for that cluster.
+
+Obviously, all controls in the cluster array must be initialized to either
+a valid control or to NULL.
+
+In rare cases you might want to know which controls of a cluster actually
+were set explicitly by the user. For this you can check the 'is_new' flag of
+each control. For example, in the case of a volume/mute cluster the 'is_new'
+flag of the mute control would be set if the user called VIDIOC_S_CTRL for
+mute only. If the user would call VIDIOC_S_EXT_CTRLS for both mute and volume
+controls, then the 'is_new' flag would be 1 for both controls.
+
+The 'is_new' flag is always 1 when called from v4l2_ctrl_handler_setup().
+
+
+Handling autogain/gain-type Controls with Auto Clusters
+-------------------------------------------------------
+
+A common type of control cluster is one that handles 'auto-foo/foo'-type
+controls. Typical examples are autogain/gain, autoexposure/exposure,
+autowhitebalance/red balance/blue balance. In all cases you have one control
+that determines whether another control is handled automatically by the hardware,
+or whether it is under manual control from the user.
+
+If the cluster is in automatic mode, then the manual controls should be
+marked inactive and volatile. When the volatile controls are read the
+g_volatile_ctrl operation should return the value that the hardware's automatic
+mode set up automatically.
+
+If the cluster is put in manual mode, then the manual controls should become
+active again and the volatile flag is cleared (so g_volatile_ctrl is no longer
+called while in manual mode). In addition just before switching to manual mode
+the current values as determined by the auto mode are copied as the new manual
+values.
+
+Finally the V4L2_CTRL_FLAG_UPDATE should be set for the auto control since
+changing that control affects the control flags of the manual controls.
+
+In order to simplify this a special variation of v4l2_ctrl_cluster was
+introduced:
+
+.. code-block:: none
+
+ void v4l2_ctrl_auto_cluster(unsigned ncontrols, struct v4l2_ctrl **controls,
+ u8 manual_val, bool set_volatile);
+
+The first two arguments are identical to v4l2_ctrl_cluster. The third argument
+tells the framework which value switches the cluster into manual mode. The
+last argument will optionally set V4L2_CTRL_FLAG_VOLATILE for the non-auto controls.
+If it is false, then the manual controls are never volatile. You would typically
+use that if the hardware does not give you the option to read back to values as
+determined by the auto mode (e.g. if autogain is on, the hardware doesn't allow
+you to obtain the current gain value).
+
+The first control of the cluster is assumed to be the 'auto' control.
+
+Using this function will ensure that you don't need to handle all the complex
+flag and volatile handling.
+
+
+VIDIOC_LOG_STATUS Support
+-------------------------
+
+This ioctl allow you to dump the current status of a driver to the kernel log.
+The v4l2_ctrl_handler_log_status(ctrl_handler, prefix) can be used to dump the
+value of the controls owned by the given handler to the log. You can supply a
+prefix as well. If the prefix didn't end with a space, then ': ' will be added
+for you.
+
+
+Different Handlers for Different Video Nodes
+--------------------------------------------
+
+Usually the V4L2 driver has just one control handler that is global for
+all video nodes. But you can also specify different control handlers for
+different video nodes. You can do that by manually setting the ctrl_handler
+field of struct video_device.
+
+That is no problem if there are no subdevs involved but if there are, then
+you need to block the automatic merging of subdev controls to the global
+control handler. You do that by simply setting the ctrl_handler field in
+struct v4l2_device to NULL. Now v4l2_device_register_subdev() will no longer
+merge subdev controls.
+
+After each subdev was added, you will then have to call v4l2_ctrl_add_handler
+manually to add the subdev's control handler (sd->ctrl_handler) to the desired
+control handler. This control handler may be specific to the video_device or
+for a subset of video_device's. For example: the radio device nodes only have
+audio controls, while the video and vbi device nodes share the same control
+handler for the audio and video controls.
+
+If you want to have one handler (e.g. for a radio device node) have a subset
+of another handler (e.g. for a video device node), then you should first add
+the controls to the first handler, add the other controls to the second
+handler and finally add the first handler to the second. For example:
+
+.. code-block:: none
+
+ v4l2_ctrl_new_std(&radio_ctrl_handler, &radio_ops, V4L2_CID_AUDIO_VOLUME, ...);
+ 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, 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:
+
+.. code-block:: none
+
+ volume = v4l2_ctrl_new_std(&video_ctrl_handler, &ops, V4L2_CID_AUDIO_VOLUME, ...);
+ v4l2_ctrl_new_std(&video_ctrl_handler, &ops, V4L2_CID_BRIGHTNESS, ...);
+ v4l2_ctrl_new_std(&video_ctrl_handler, &ops, V4L2_CID_CONTRAST, ...);
+
+What you should not do is make two identical controls for two handlers.
+For example:
+
+.. code-block:: none
+
+ v4l2_ctrl_new_std(&radio_ctrl_handler, &radio_ops, V4L2_CID_AUDIO_MUTE, ...);
+ v4l2_ctrl_new_std(&video_ctrl_handler, &video_ops, V4L2_CID_AUDIO_MUTE, ...);
+
+This would be bad since muting the radio would not change the video mute
+control. The rule is to have one control for each hardware 'knob' that you
+can twiddle.
+
+
+Finding Controls
+----------------
+
+Normally you have created the controls yourself and you can store the struct
+v4l2_ctrl pointer into your own struct.
+
+But sometimes you need to find a control from another handler that you do
+not own. For example, if you have to find a volume control from a subdev.
+
+You can do that by calling v4l2_ctrl_find:
+
+.. code-block:: none
+
+ struct v4l2_ctrl *volume;
+
+ volume = v4l2_ctrl_find(sd->ctrl_handler, V4L2_CID_AUDIO_VOLUME);
+
+Since v4l2_ctrl_find will lock the handler you have to be careful where you
+use it. For example, this is not a good idea:
+
+.. code-block:: none
+
+ struct v4l2_ctrl_handler ctrl_handler;
+
+ v4l2_ctrl_new_std(&ctrl_handler, &video_ops, V4L2_CID_BRIGHTNESS, ...);
+ v4l2_ctrl_new_std(&ctrl_handler, &video_ops, V4L2_CID_CONTRAST, ...);
+
+...and in video_ops.s_ctrl:
+
+.. code-block:: none
+
+ case V4L2_CID_BRIGHTNESS:
+ contrast = v4l2_find_ctrl(&ctrl_handler, V4L2_CID_CONTRAST);
+ ...
+
+When s_ctrl is called by the framework the ctrl_handler.lock is already taken, so
+attempting to find another control from the same handler will deadlock.
+
+It is recommended not to use this function from inside the control ops.
+
+
+Inheriting Controls
+-------------------
+
+When one control handler is added to another using v4l2_ctrl_add_handler, then
+by default all controls from one are merged to the other. But a subdev might
+have low-level controls that make sense for some advanced embedded system, but
+not when it is used in consumer-level hardware. In that case you want to keep
+those low-level controls local to the subdev. You can do this by simply
+setting the 'is_private' flag of the control to 1:
+
+.. code-block:: none
+
+ static const struct v4l2_ctrl_config ctrl_private = {
+ .ops = &ctrl_custom_ops,
+ .id = V4L2_CID_...,
+ .name = "Some Private Control",
+ .type = V4L2_CTRL_TYPE_INTEGER,
+ .max = 15,
+ .step = 1,
+ .is_private = 1,
+ };
+
+ ctrl = v4l2_ctrl_new_custom(&foo->ctrl_handler, &ctrl_private, NULL);
+
+These controls will now be skipped when v4l2_ctrl_add_handler is called.
+
+
+V4L2_CTRL_TYPE_CTRL_CLASS Controls
+----------------------------------
+
+Controls of this type can be used by GUIs to get the name of the control class.
+A fully featured GUI can make a dialog with multiple tabs with each tab
+containing the controls belonging to a particular control class. The name of
+each tab can be found by querying a special control with ID <control class | 1>.
+
+Drivers do not have to care about this. The framework will automatically add
+a control of this type whenever the first control belonging to a new control
+class is added.
+
+
+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:
+
+.. code-block:: none
+
+ void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl,
+ void (*notify)(struct v4l2_ctrl *ctrl, void *priv), void *priv);
+
+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.
+
+There can be only one notify function per control handler. Any attempt
+to set another notify function will cause a WARN_ON.
/*
* demux.h
*
+ * The Kernel Digital TV Demux kABI defines a driver-internal interface for
+ * registering low-level, hardware specific driver to a hardware independent
+ * demux layer.
+ *
* Copyright (c) 2002 Convergence GmbH
*
* based on code:
#include <linux/time.h>
#include <linux/dvb/dmx.h>
-/**
- * DOC: Digital TV Demux
- *
- * The Kernel Digital TV Demux kABI defines a driver-internal interface for
- * registering low-level, hardware specific driver to a hardware independent
- * demux layer. It is only of interest for Digital TV device driver writers.
- * The header file for this kABI is named demux.h and located in
- * drivers/media/dvb-core.
- *
- * The demux kABI should be implemented for each demux in the system. It is
- * used to select the TS source of a demux and to manage the demux resources.
- * When the demux client allocates a resource via the demux kABI, it receives
- * a pointer to the kABI of that resource.
- *
- * Each demux receives its TS input from a DVB front-end or from memory, as
- * set via this demux kABI. In a system with more than one front-end, the kABI
- * can be used to select one of the DVB front-ends as a TS source for a demux,
- * unless this is fixed in the HW platform.
- *
- * The demux kABI only controls front-ends regarding to their connections with
- * demuxes; the kABI used to set the other front-end parameters, such as
- * tuning, are devined via the Digital TV Frontend kABI.
- *
- * The functions that implement the abstract interface demux should be defined
- * static or module private and registered to the Demux core for external
- * access. It is not necessary to implement every function in the struct
- * &dmx_demux. For example, a demux interface might support Section filtering,
- * but not PES filtering. The kABI client is expected to check the value of any
- * function pointer before calling the function: the value of NULL means
- * that the function is not available.
- *
- * Whenever the functions of the demux API modify shared data, the
- * possibilities of lost update and race condition problems should be
- * addressed, e.g. by protecting parts of code with mutexes.
- *
- * Note that functions called from a bottom half context must not sleep.
- * Even a simple memory allocation without using %GFP_ATOMIC can result in a
- * kernel thread being put to sleep if swapping is needed. For example, the
- * Linux Kernel calls the functions of a network device interface from a
- * bottom half context. Thus, if a demux kABI function is called from network
- * device code, the function must not sleep.
- */
-
/*
* Common definitions
*/
int type,
enum dmx_ts_pes pes_type,
size_t circular_buffer_size,
- struct timespec timeout);
+ ktime_t timeout);
int (*start_filtering)(struct dmx_ts_feed *feed);
int (*stop_filtering)(struct dmx_ts_feed *feed);
};
int (*stop_filtering)(struct dmx_section_feed *feed);
};
-/**
- * DOC: Demux Callback
- *
- * This kernel-space API comprises the callback functions that deliver filtered
- * data to the demux client. Unlike the other DVB kABIs, these functions are
- * provided by the client and called from the demux code.
- *
- * The function pointers of this abstract interface are not packed into a
- * structure as in the other demux APIs, because the callback functions are
- * registered and used independent of each other. As an example, it is possible
- * for the API client to provide several callback functions for receiving TS
- * packets and no callbacks for PES packets or sections.
- *
- * The functions that implement the callback API need not be re-entrant: when
- * a demux driver calls one of these functions, the driver is not allowed to
- * call the function again before the original call returns. If a callback is
- * triggered by a hardware interrupt, it is recommended to use the Linux
- * bottom half mechanism or start a tasklet instead of making the callback
- * function call directly from a hardware interrupt.
- *
- * This mechanism is implemented by dmx_ts_cb() and dmx_section_cb()
- * callbacks.
- */
-
/**
* typedef dmx_ts_cb - DVB demux TS filter callback function prototype
*
* @open is called and decrement it when @close is called.
* The @demux function parameter contains a pointer to the demux API and
* instance data.
- * It returns
- * 0 on success;
- * -EUSERS, if maximum usage count was reached;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EUSERS, if maximum usage count was reached;
+ * -EINVAL, on bad parameter.
*
* @close: This function reserves the demux for use by the caller and, if
* necessary, initializes the demux. When the demux is no longer needed,
* @open is called and decrement it when @close is called.
* The @demux function parameter contains a pointer to the demux API and
* instance data.
- * It returns
- * 0 on success;
- * -ENODEV, if demux was not in use (e. g. no users);
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -ENODEV, if demux was not in use (e. g. no users);
+ * -EINVAL, on bad parameter.
*
* @write: This function provides the demux driver with a memory buffer
* containing TS packets. Instead of receiving TS packets from the DVB
* The @buf function parameter contains a pointer to the TS data in
* kernel-space memory.
* The @count function parameter contains the length of the TS data.
- * It returns
- * 0 on success;
- * -ERESTARTSYS, if mutex lock was interrupted;
- * -EINTR, if a signal handling is pending;
- * -ENODEV, if demux was removed;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -ERESTARTSYS, if mutex lock was interrupted;
+ * -EINTR, if a signal handling is pending;
+ * -ENODEV, if demux was removed;
+ * -EINVAL, on bad parameter.
*
* @allocate_ts_feed: Allocates a new TS feed, which is used to filter the TS
* packets carrying a certain PID. The TS feed normally corresponds to a
* instance data.
* The @callback function parameter contains a pointer to the callback
* function for passing received TS packet.
- * It returns
- * 0 on success;
- * -ERESTARTSYS, if mutex lock was interrupted;
- * -EBUSY, if no more TS feeds is available;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -ERESTARTSYS, if mutex lock was interrupted;
+ * -EBUSY, if no more TS feeds is available;
+ * -EINVAL, on bad parameter.
*
* @release_ts_feed: Releases the resources allocated with @allocate_ts_feed.
* Any filtering in progress on the TS feed should be stopped before
* instance data.
* The @feed function parameter contains a pointer to the TS feed API and
* instance data.
- * It returns
- * 0 on success;
- * -EINVAL on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL on bad parameter.
*
* @allocate_section_feed: Allocates a new section feed, i.e. a demux resource
* for filtering and receiving sections. On platforms with hardware
* instance data.
* The @callback function parameter contains a pointer to the callback
* function for passing received TS packet.
- * It returns
- * 0 on success;
- * -EBUSY, if no more TS feeds is available;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EBUSY, if no more TS feeds is available;
+ * -EINVAL, on bad parameter.
*
* @release_section_feed: Releases the resources allocated with
* @allocate_section_feed, including allocated filters. Any filtering in
* instance data.
* The @feed function parameter contains a pointer to the TS feed API and
* instance data.
- * It returns
- * 0 on success;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL, on bad parameter.
*
* @add_frontend: Registers a connectivity between a demux and a front-end,
* i.e., indicates that the demux can be connected via a call to
* instance data.
* The @frontend function parameter contains a pointer to the front-end
* instance data.
- * It returns
- * 0 on success;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL, on bad parameter.
*
* @remove_frontend: Indicates that the given front-end, registered by a call
* to @add_frontend, can no longer be connected as a TS source by this
* instance data.
* The @frontend function parameter contains a pointer to the front-end
* instance data.
- * It returns
- * 0 on success;
- * -ENODEV, if the front-end was not found,
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -ENODEV, if the front-end was not found,
+ * -EINVAL, on bad parameter.
*
* @get_frontends: Provides the APIs of the front-ends that have been
* registered for this demux. Any of the front-ends obtained with this
* instance data.
* The @frontend function parameter contains a pointer to the front-end
* instance data.
- * It returns
- * 0 on success;
- * -EINVAL, on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL, on bad parameter.
*
* @disconnect_frontend: Disconnects the demux and a front-end previously
* connected by a @connect_frontend call.
* The @demux function parameter contains a pointer to the demux API and
* instance data.
- * It returns
- * 0 on success;
- * -EINVAL on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL on bad parameter.
*
* @get_pes_pids: Get the PIDs for DMX_PES_AUDIO0, DMX_PES_VIDEO0,
* DMX_PES_TELETEXT0, DMX_PES_SUBTITLE0 and DMX_PES_PCR0.
* instance data.
* The @pids function parameter contains an array with five u16 elements
* where the PIDs will be stored.
- * It returns
- * 0 on success;
- * -EINVAL on bad parameter.
+ * It returns:
+ * 0 on success;
+ * -EINVAL on bad parameter.
*/
struct dmx_demux {
VB2_MEMORY_DMABUF = 4,
};
- struct vb2_alloc_ctx;
struct vb2_fileio_data;
struct vb2_threadio_data;
* @put_userptr: inform the allocator that a USERPTR buffer will no longer
* be used.
* @attach_dmabuf: attach a shared struct dma_buf for a hardware operation;
- * used for DMABUF memory types; alloc_ctx is the alloc context
+ * used for DMABUF memory types; dev is the alloc device
* dbuf is the shared dma_buf; returns NULL on failure;
* allocator private per-buffer structure on success;
* this needs to be used for further accesses to the buffer.
* @mmap: setup a userspace mapping for a given memory buffer under
* the provided virtual memory region.
*
- * Required ops for USERPTR types: get_userptr, put_userptr.
- * Required ops for MMAP types: alloc, put, num_users, mmap.
- * Required ops for read/write access types: alloc, put, num_users, vaddr.
- * Required ops for DMABUF types: attach_dmabuf, detach_dmabuf, map_dmabuf,
- * unmap_dmabuf.
+ * Those operations are used by the videobuf2 core to implement the memory
+ * handling/memory allocators for each type of supported streaming I/O method.
+ *
+ * .. note::
+ * #) Required ops for USERPTR types: get_userptr, put_userptr.
+ *
+ * #) Required ops for MMAP types: alloc, put, num_users, mmap.
+ *
+ * #) Required ops for read/write access types: alloc, put, num_users, vaddr.
+ *
+ * #) Required ops for DMABUF types: attach_dmabuf, detach_dmabuf, map_dmabuf, unmap_dmabuf.
*/
struct vb2_mem_ops {
- void *(*alloc)(void *alloc_ctx, unsigned long size,
- enum dma_data_direction dma_dir,
+ void *(*alloc)(struct device *dev, const struct dma_attrs *attrs,
+ unsigned long size, enum dma_data_direction dma_dir,
gfp_t gfp_flags);
void (*put)(void *buf_priv);
struct dma_buf *(*get_dmabuf)(void *buf_priv, unsigned long flags);
- void *(*get_userptr)(void *alloc_ctx, unsigned long vaddr,
+ void *(*get_userptr)(struct device *dev, unsigned long vaddr,
unsigned long size,
enum dma_data_direction dma_dir);
void (*put_userptr)(void *buf_priv);
void (*prepare)(void *buf_priv);
void (*finish)(void *buf_priv);
- void *(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf,
+ void *(*attach_dmabuf)(struct device *dev, struct dma_buf *dbuf,
unsigned long size,
enum dma_data_direction dma_dir);
void (*detach_dmabuf)(void *buf_priv);
* second time with the actually allocated number of
* buffers to verify if that is OK.
* The driver should return the required number of buffers
- * in *num_buffers, the required number of planes per
- * buffer in *num_planes, the size of each plane should be
+ * in \*num_buffers, the required number of planes per
+ * buffer in \*num_planes, the size of each plane should be
* set in the sizes[] array and optional per-plane
- * allocator specific context in the alloc_ctxs[] array.
- * When called from VIDIOC_REQBUFS, \*num_planes == 0, the
+ * allocator specific device in the alloc_devs[] array.
+ * When called from VIDIOC_REQBUFS, *num_planes == 0, the
* driver has to use the currently configured format to
- * determine the plane sizes and *num_buffers is the total
+ * determine the plane sizes and \*num_buffers is the total
* number of buffers that are being allocated. When called
- * from VIDIOC_CREATE_BUFS, *num_planes != 0 and it
+ * from VIDIOC_CREATE_BUFS, \*num_planes != 0 and it
* describes the requested number of planes and sizes[]
* contains the requested plane sizes. If either
- * *num_planes or the requested sizes are invalid callback
- * must return -EINVAL. In this case *num_buffers are
+ * \*num_planes or the requested sizes are invalid callback
+ * must return -EINVAL. In this case \*num_buffers are
* being allocated additionally to q->num_buffers.
* @wait_prepare: release any locks taken while calling vb2 functions;
* it is called before an ioctl needs to wait for a new
struct vb2_ops {
int (*queue_setup)(struct vb2_queue *q,
unsigned int *num_buffers, unsigned int *num_planes,
- unsigned int sizes[], void *alloc_ctxs[]);
+ unsigned int sizes[], struct device *alloc_devs[]);
void (*wait_prepare)(struct vb2_queue *q);
void (*wait_finish)(struct vb2_queue *q);
* caller. For example, for V4L2, it should match
* the V4L2_BUF_TYPE_* in include/uapi/linux/videodev2.h
* @io_modes: supported io methods (see vb2_io_modes enum)
+ * @dev: device to use for the default allocation context if the driver
+ * doesn't fill in the @alloc_devs array.
+ * @dma_attrs: DMA attributes to use for the DMA. May be NULL.
* @fileio_read_once: report EOF after reading the first buffer
* @fileio_write_immediately: queue buffer after each write() call
* @allow_zero_bytesused: allow bytesused == 0 to be passed to the driver
* @done_list: list of buffers ready to be dequeued to userspace
* @done_lock: lock to protect done_list list
* @done_wq: waitqueue for processes waiting for buffers ready to be dequeued
- * @alloc_ctx: memory type/allocator-specific contexts for each plane
+ * @alloc_devs: memory type/allocator-specific per-plane device
* @streaming: current streaming state
* @start_streaming_called: start_streaming() was called successfully and we
* started streaming.
struct vb2_queue {
unsigned int type;
unsigned int io_modes;
+ struct device *dev;
+ const struct dma_attrs *dma_attrs;
unsigned fileio_read_once:1;
unsigned fileio_write_immediately:1;
unsigned allow_zero_bytesused:1;
spinlock_t done_lock;
wait_queue_head_t done_wq;
- void *alloc_ctx[VB2_MAX_PLANES];
+ struct device *alloc_devs[VB2_MAX_PLANES];
unsigned int streaming:1;
unsigned int start_streaming_called:1;
projects / mirror_ubuntu-artful-kernel.git / commitdiff