[PATCH v2 1/2] v4l: Add camera voice coil lens control class, current control

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Add a V4L2 control class for voice coil lens driver devices. These are
simple devices that are used to move a camera lens from its resting
position.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 Documentation/media/uapi/v4l/extended-controls.rst | 28 ++++++++++++++++++++++
 drivers/media/i2c/ad5820.c                         |  3 +++
 include/uapi/linux/v4l2-controls.h                 |  9 ++++++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Documentation/media/uapi/v4l/extended-controls.rst b/Documentation/media/uapi/v4l/extended-controls.rst
index abb1057..a75451a 100644
--- a/Documentation/media/uapi/v4l/extended-controls.rst
+++ b/Documentation/media/uapi/v4l/extended-controls.rst
@@ -3022,6 +3022,34 @@ Image Process Control IDs
     driver specific and are documented in :ref:`v4l-drivers`.
 
 
+.. _voice-coil-lens-controls:
+
+Voice Coil Lens Control Reference
+=================================
+
+The Voice Coil class controls are used to control voice coil lens
+devices. These are very simple devices that consist of a voice coil, a
+spring and a lens. The current applied on the voice coil is used to
+move the lens away from the resting position which typically is (close
+to) infinity. The higher the current applied, the closer the lens is
+typically focused.
+
+.. _voice-coil-lens-control-is:
+
+Voice Coil Lens Control IDs
+---------------------------
+
+``V4L2_CID_VOICE_COIL_CLASS (class)``
+    The VOICE_COIL class descriptor.
+
+``V4L2_CID_VOICE_COIL_CURRENT (integer)``
+    Current applied on a voice coil. The more current is applied, the
+    more is the position of the lens moved from its resting position.
+    Do note that there may be a ringing effect; the lens will
+    oscillate after changing the current applied unless the device
+    implements ringing compensation.
+
+
 .. _dv-controls:
 
 Digital Video Control Reference
diff --git a/drivers/media/i2c/ad5820.c b/drivers/media/i2c/ad5820.c
index a9026a91..7167b26 100644
--- a/drivers/media/i2c/ad5820.c
+++ b/drivers/media/i2c/ad5820.c
@@ -162,6 +162,7 @@ static int ad5820_set_ctrl(struct v4l2_ctrl *ctrl)
 
 	switch (ctrl->id) {
 	case V4L2_CID_FOCUS_ABSOLUTE:
+	case V4L2_CID_VOICE_COIL_CURRENT:
 		coil->focus_absolute = ctrl->val;
 		return ad5820_update_hw(coil);
 	}
@@ -192,6 +193,8 @@ static int ad5820_init_controls(struct ad5820_device *coil)
 	 */
 	v4l2_ctrl_new_std(&coil->ctrls, &ad5820_ctrl_ops,
 			  V4L2_CID_FOCUS_ABSOLUTE, 0, 1023, 1, 0);
+	v4l2_ctrl_new_std(&coil->ctrls, &ad5820_ctrl_ops,
+			  V4L2_CID_VOICE_COIL_CURRENT, 0, 1023, 1, 0);
 
 	if (coil->ctrls.error)
 		return coil->ctrls.error;
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 0d2e1e0..c1efbc5 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -62,7 +62,7 @@
 #define V4L2_CTRL_CLASS_FM_RX		0x00a10000	/* FM Receiver controls */
 #define V4L2_CTRL_CLASS_RF_TUNER	0x00a20000	/* RF tuner controls */
 #define V4L2_CTRL_CLASS_DETECT		0x00a30000	/* Detection controls */
-
+#define V4L2_CTRL_CLASS_VOICE_COIL	0x00a40000	/* Voice coil lens driver controls */
 /* User-class control IDs */
 
 #define V4L2_CID_BASE			(V4L2_CTRL_CLASS_USER | 0x900)
@@ -894,6 +894,13 @@ enum v4l2_jpeg_chroma_subsampling {
 #define V4L2_CID_TEST_PATTERN			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
 #define V4L2_CID_DEINTERLACING_MODE		(V4L2_CID_IMAGE_PROC_CLASS_BASE + 4)
 
+/* Voice coil lens driver controls */
+
+#define V4L2_CID_VOICE_COIL_CLASS_BASE		(V4L2_CTRL_CLASS_VOICE_COIL | 0x900)
+#define V4L2_CID_VOICE_COIL_CLASS		(V4L2_CTRL_CLASS_VOICE_COIL | 1)
+
+#define V4L2_CID_VOICE_COIL_CURRENT		(V4L2_CID_VOICE_COIL_CLASS_BASE + 1)
+
 
 /*  DV-class control IDs defined by V4L2 */
 #define V4L2_CID_DV_CLASS_BASE			(V4L2_CTRL_CLASS_DV | 0x900)
-- 
2.7.4