[PATCH v4] media: i2c: ov13858: add horizontal and vertical flip controls

[Sergey Lebedev <lsa.uz@pm.me>]

The Microsoft Surface Pro 11 for Business (Intel) mounts this sensor
upside down, as commit b238116ccd4b ("media: ipu-bridge: Add upside-down
quirk for Surface Pro 11") records, and the driver has no flip controls
to compensate.

Add V4L2_CID_HFLIP and V4L2_CID_VFLIP on bits 3 and 4 of register 0x3820.
The mirror bit is active low, as in Intel's out-of-tree ov13858 driver.
The Bayer order does not change with either flip, so the controls do not
set V4L2_CTRL_FLAG_MODIFY_LAYOUT. They are clustered, and grabbed while
streaming.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Sergey Lebedev <lsa.uz@pm.me>
Tested-by: German Pablo Lindo <germanpapulindez@gmail.com>
---
v4:
 - The comment on 0x3820 now sits on the horizontal flip bit, the only
   one it is true of. (Sakari)
 - Commit message rewritten shorter. (Sakari)
 - Assisted-by added, per Documentation/process/coding-assistants.rst.

Only a comment changed in the code, so German's Tested-by is kept.

v3: https://lore.kernel.org/all/20260926080242.93628-1-lsa.uz@pm.me/
v2: https://lore.kernel.org/all/20260921124444.79396-1-lsa.uz@pm.me/
v1: https://lore.kernel.org/all/20260921082609.30830-1-lsa.uz@pm.me/

 drivers/media/i2c/ov13858.c | 50 +++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/media/i2c/ov13858.c b/drivers/media/i2c/ov13858.c
index de2b79a9a0e..5a49fa0ec02 100644
--- a/drivers/media/i2c/ov13858.c
+++ b/drivers/media/i2c/ov13858.c
@@ -76,6 +76,12 @@
 #define OV13858_DGTL_GAIN_DEFAULT	1024	/* Default gain = 1 X */
 #define OV13858_DGTL_GAIN_STEP		1	/* Each step = 1/1024 */
 
+/* Readout direction */
+#define OV13858_REG_FORMAT1		0x3820
+#define OV13858_FORMAT1_VFLIP		BIT(4)
+/* Horizontal flip, active low: every mode table sets this bit */
+#define OV13858_FORMAT1_HFLIP_N		BIT(3)
+
 /* Test Pattern Control */
 #define OV13858_REG_TEST_PATTERN	0x4503
 #define OV13858_TEST_PATTERN_ENABLE	BIT(7)
@@ -1042,6 +1048,8 @@ struct ov13858 {
 	struct v4l2_ctrl *vblank;
 	struct v4l2_ctrl *hblank;
 	struct v4l2_ctrl *exposure;
+	struct v4l2_ctrl *hflip;
+	struct v4l2_ctrl *vflip;
 
 	/* Current mode */
 	const struct ov13858_mode *cur_mode;
@@ -1208,6 +1216,31 @@ static int ov13858_enable_test_pattern(struct ov13858 *ov13858, u32 pattern)
 				 OV13858_REG_VALUE_08BIT, val);
 }
 
+static int ov13858_update_flips(struct ov13858 *ov13858)
+{
+	u32 val;
+	int ret;
+
+	ret = ov13858_read_reg(ov13858, OV13858_REG_FORMAT1,
+			       OV13858_REG_VALUE_08BIT, &val);
+	if (ret)
+		return ret;
+
+	if (ov13858->vflip->val)
+		val |= OV13858_FORMAT1_VFLIP;
+	else
+		val &= ~OV13858_FORMAT1_VFLIP;
+
+	/* The mirror bit is active low, as it is on ov13b10. */
+	if (ov13858->hflip->val)
+		val &= ~OV13858_FORMAT1_HFLIP_N;
+	else
+		val |= OV13858_FORMAT1_HFLIP_N;
+
+	return ov13858_write_reg(ov13858, OV13858_REG_FORMAT1,
+				 OV13858_REG_VALUE_08BIT, val);
+}
+
 static int ov13858_set_ctrl(struct v4l2_ctrl *ctrl)
 {
 	struct ov13858 *ov13858 = container_of(ctrl->handler,
@@ -1254,6 +1287,10 @@ static int ov13858_set_ctrl(struct v4l2_ctrl *ctrl)
 					ov13858->cur_mode->height
 					  + ctrl->val);
 		break;
+	case V4L2_CID_HFLIP:
+	case V4L2_CID_VFLIP:
+		ret = ov13858_update_flips(ov13858);
+		break;
 	case V4L2_CID_TEST_PATTERN:
 		ret = ov13858_enable_test_pattern(ov13858, ctrl->val);
 		break;
@@ -1481,6 +1518,13 @@ static int ov13858_set_stream(struct v4l2_subdev *sd, int enable)
 		pm_runtime_put(ov13858->dev);
 	}
 
+	/*
+	 * Do not let the flips change while streaming. ov13858->mutex is the
+	 * control handler's own lock and is held here, hence the __ form.
+	 */
+	__v4l2_ctrl_grab(ov13858->hflip, enable);
+	__v4l2_ctrl_grab(ov13858->vflip, enable);
+
 	mutex_unlock(&ov13858->mutex);
 
 	return ret;
@@ -1619,6 +1663,12 @@ static int ov13858_init_controls(struct ov13858 *ov13858)
 			  OV13858_DGTL_GAIN_MIN, OV13858_DGTL_GAIN_MAX,
 			  OV13858_DGTL_GAIN_STEP, OV13858_DGTL_GAIN_DEFAULT);
 
+	ov13858->hflip = v4l2_ctrl_new_std(ctrl_hdlr, &ov13858_ctrl_ops,
+					   V4L2_CID_HFLIP, 0, 1, 1, 0);
+	ov13858->vflip = v4l2_ctrl_new_std(ctrl_hdlr, &ov13858_ctrl_ops,
+					   V4L2_CID_VFLIP, 0, 1, 1, 0);
+	v4l2_ctrl_cluster(2, &ov13858->hflip);
+
 	v4l2_ctrl_new_std_menu_items(ctrl_hdlr, &ov13858_ctrl_ops,
 				     V4L2_CID_TEST_PATTERN,
 				     ARRAY_SIZE(ov13858_test_pattern_menu) - 1,
-- 
2.54.0 (Apple Git-157)