[PATCH v3] media: v4l2-ctrl: add a helper function to modify the menu

[Prabhakar Lad]

From: Lad, Prabhakar <prabhakar.lad@xxxxxx>

Add a helper function to modify the menu, max and default value
to set.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@xxxxxx>
Signed-off-by: Manjunath Hadli <manjunath.hadli@xxxxxx>
Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Sakari Ailus <sakari.ailus@xxxxxx>
Cc: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
Cc: Rob Landley <rob@xxxxxxxxxxx>
---
Changes for v3:
1: Fixed style/grammer issues as pointed by Hans.
   Thanks Hans for providing the description.

Changes for v2:
1: Fixed review comments from Hans, to have return type as
   void, add WARN_ON() for fail conditions, allow this fucntion
   to modify the menu of custom controls.

 Documentation/video4linux/v4l2-controls.txt |   29 +++++++++++++++++++++++++++
 drivers/media/v4l2-core/v4l2-ctrls.c        |   17 +++++++++++++++
 include/media/v4l2-ctrls.h                  |   11 ++++++++++
 3 files changed, 57 insertions(+), 0 deletions(-)

diff --git a/Documentation/video4linux/v4l2-controls.txt b/Documentation/video4linux/v4l2-controls.txt
index 43da22b..01d0a82 100644
--- a/Documentation/video4linux/v4l2-controls.txt
+++ b/Documentation/video4linux/v4l2-controls.txt
@@ -367,6 +367,35 @@ 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().
 
+There are situations where menu items may be device specific. In such cases the
+framework provides a helper function to change the menu:
+
+void v4l2_ctrl_modify_menu(struct v4l2_ctrl *ctrl, const char * const *qmenu,
+	s32 max, u32 menu_skip_mask, s32 def);
+
+A good example 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.
+
+This helper function is used to modify the menu, max, mask and the default
+value of the control.
+
+Example:
+
+	static const char * const test_pattern[] = {
+		"Disabled",
+		"Vertical Bars",
+		"Solid Black",
+		"Solid White",
+		NULL,
+	};
+	struct v4l2_ctrl *test_pattern_ctrl =
+		v4l2_ctrl_new_std_menu(&foo->ctrl_handler, &foo_ctrl_ops,
+			V4L2_CID_TEST_PATTERN, V4L2_TEST_PATTERN_DISABLED, 0,
+			V4L2_TEST_PATTERN_DISABLED);
+
+	v4l2_ctrl_modify_menu(test_pattern_ctrl, test_pattern, 3, 0,
+		V4L2_TEST_PATTERN_DISABLED);
 
 Custom Controls
 ===============
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index d731422..d89b460 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -2666,3 +2666,20 @@ unsigned int v4l2_ctrl_poll(struct file *file, struct poll_table_struct *wait)
 	return 0;
 }
 EXPORT_SYMBOL(v4l2_ctrl_poll);
+
+/* Helper function for modifying the menu */
+void v4l2_ctrl_modify_menu(struct v4l2_ctrl *ctrl, const char * const *qmenu,
+			   s32 max, u32 menu_skip_mask, s32 def)
+{
+	if (WARN_ON(ctrl->type != V4L2_CTRL_TYPE_MENU || qmenu == NULL))
+		return;
+
+	if (WARN_ON(def < 0 || def > max))
+		return;
+
+	ctrl->qmenu = qmenu;
+	ctrl->maximum = max;
+	ctrl->menu_skip_mask = menu_skip_mask;
+	ctrl->cur.val = ctrl->val = ctrl->default_value = def;
+}
+EXPORT_SYMBOL(v4l2_ctrl_modify_menu);
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index 776605f..5303489 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -488,6 +488,17 @@ static inline void v4l2_ctrl_unlock(struct v4l2_ctrl *ctrl)
 	mutex_unlock(ctrl->handler->lock);
 }
 
+/**
+ * v4l2_ctrl_modify_menu() - This function is used to modify the menu.
+ * @ctrl:		The control whose menu should be modified.
+ * @qmenu:		The new menu.
+ * @max:		Maximum value of the control.
+ * @menu_skip_mask:	The control's skip mask for menu controls.
+ * @def:		The default value for control to be set.
+ */
+void v4l2_ctrl_modify_menu(struct v4l2_ctrl *ctrl, const char * const *qmenu,
+			   s32 max, u32 menu_skip_mask, s32 def);
+
 /** v4l2_ctrl_g_ctrl() - Helper function to get the control's value from within a driver.
   * @ctrl:	The control.
   *
-- 
1.7.0.4

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