v4l: Add camera voice coil lens control class, current control

v4l: Add camera voice coil lens control class, current control

[Sakari Ailus]

Hi folks,

I wanted to refresh my voice coil lens patchset before we have more voice
coil lens controller drivers. The VOCUS_ABSOLUTE control really is not a
best control ID to control a voice coil driver's current.

There may be additional controls in the class: the hardware I'm familiar
with provides other controls (PWM vs. linear mode, resonance frequency and
ringing compensation formula to name a few) but I'm not fully certain
they're something that even should be told to the user --- let alone
giving the user write access to them.

My expectation is still that there will be more controls in the class. The
PWM / linear mode might be one candidate: PWM saves power but it may cause
other issues. These other issues might be something to ignore, depending
on the use case. That will be anyway left for the future.

-- 
Kind regards,
Sakari

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

[Sakari Ailus]

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

[PATCH v2 2/2] ad5820: Use VOICE_COIL_CURRENT control

[Sakari Ailus]

Add V4L2_CID_VOICE_COIL_CURRENT control support to the ad5820 driver. The
usage of the control is equivalent to how V4L2_CID_FOCUS_ABSOLUTE was used
by the driver. The old control remains supported.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 drivers/media/i2c/ad5820.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/media/i2c/ad5820.c b/drivers/media/i2c/ad5820.c
index 7167b26..e5ff1a2 100644
--- a/drivers/media/i2c/ad5820.c
+++ b/drivers/media/i2c/ad5820.c
@@ -51,7 +51,7 @@ struct ad5820_device {
 	struct regulator *vana;
 
 	struct v4l2_ctrl_handler ctrls;
-	u32 focus_absolute;
+	struct v4l2_ctrl *focus, *curr;
 	u32 focus_ramp_time;
 	u32 focus_ramp_mode;
 
@@ -59,6 +59,7 @@ struct ad5820_device {
 	int power_count;
 
 	bool standby;
+	bool in_set_ctrl;
 };
 
 static int ad5820_write(struct ad5820_device *coil, u16 data)
@@ -98,7 +99,7 @@ static int ad5820_update_hw(struct ad5820_device *coil)
 	status = RAMP_US_TO_CODE(coil->focus_ramp_time);
 	status |= coil->focus_ramp_mode
 		? AD5820_RAMP_MODE_64_16 : AD5820_RAMP_MODE_LINEAR;
-	status |= coil->focus_absolute << AD5820_DAC_SHIFT;
+	status |= coil->curr->val << AD5820_DAC_SHIFT;
 
 	if (coil->standby)
 		status |= AD5820_POWER_DOWN;
@@ -160,10 +161,16 @@ static int ad5820_set_ctrl(struct v4l2_ctrl *ctrl)
 	struct ad5820_device *coil =
 		container_of(ctrl->handler, struct ad5820_device, ctrls);
 
+	if (coil->in_set_ctrl)
+		return 0;
+
 	switch (ctrl->id) {
 	case V4L2_CID_FOCUS_ABSOLUTE:
 	case V4L2_CID_VOICE_COIL_CURRENT:
-		coil->focus_absolute = ctrl->val;
+		coil->in_set_ctrl = true;
+		__v4l2_ctrl_s_ctrl(ctrl == coil->focus ?
+				   coil->curr : coil->focus, ctrl->val);
+		coil->in_set_ctrl = false;
 		return ad5820_update_hw(coil);
 	}
 
@@ -190,16 +197,21 @@ static int ad5820_init_controls(struct ad5820_device *coil)
 	 * will just use abstract codes here. In any case, smaller value = focus
 	 * position farther from camera. The default zero value means focus at
 	 * infinity, and also least current consumption.
+	 *
+	 * The two controls below control the current. The
+	 * FOCUS_ABSOLUTE is there for compatibility with old user
+	 * space whereas the VOICE_COIL_CURRENT should be used by both
+	 * new applications and drivers.
 	 */
-	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);
+	coil->focus = v4l2_ctrl_new_std(&coil->ctrls, &ad5820_ctrl_ops,
+					V4L2_CID_FOCUS_ABSOLUTE, 0, 1023, 1, 0);
+	coil->curr = 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;
 
-	coil->focus_absolute = 0;
 	coil->focus_ramp_time = 0;
 	coil->focus_ramp_mode = 0;
 
-- 
2.7.4