[PATCH] media: vimc: add support for V4L2_FIELD_ALTERNATE in vimc-sensor

[Pavan Bobba <opensource206@gmail.com>]

The vimc sensor currently ignores V4L2_FIELD_ALTERNATE and always
configures the test pattern generator (TPG) with a progressive field.
This patch adds basic handling for the ALTERNATE field type.

When userspace requests V4L2_FIELD_ALTERNATE, the TPG is configured
to output alternating top and bottom fields by calling tpg_s_field()
with the interlaced flag set. For all other field types, existing
progressive behaviour is preserved.

This change allows the vimc-sensor subdevice to correctly reflect
the requested field type in its reported format, enabling basic
testing of interlaced-field negotiation in the media pipeline.
Other vimc entities (debayer, scaler, capture) still treat all
streams as progressive, so streaming with ALTERNATE may not yet
succeed.

Signed-off-by: Pavan Bobba <opensource206@gmail.com>
---
 drivers/media/test-drivers/vimc/vimc-sensor.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/media/test-drivers/vimc/vimc-sensor.c b/drivers/media/test-drivers/vimc/vimc-sensor.c
index 027767777763..900c3f329f1c 100644
--- a/drivers/media/test-drivers/vimc/vimc-sensor.c
+++ b/drivers/media/test-drivers/vimc/vimc-sensor.c
@@ -105,8 +105,10 @@ static void vimc_sensor_tpg_s_format(struct vimc_sensor_device *vsensor,
 	tpg_s_bytesperline(&vsensor->tpg, 0, format->width * vpix->bpp);
 	tpg_s_buf_height(&vsensor->tpg, format->height);
 	tpg_s_fourcc(&vsensor->tpg, vpix->pixelformat);
-	/* TODO: add support for V4L2_FIELD_ALTERNATE */
-	tpg_s_field(&vsensor->tpg, format->field, false);
+	if (format->field == V4L2_FIELD_ALTERNATE)
+		tpg_s_field(&vsensor->tpg, V4L2_FIELD_TOP, true);
+	else
+		tpg_s_field(&vsensor->tpg, format->field, false);
 	tpg_s_colorspace(&vsensor->tpg, format->colorspace);
 	tpg_s_ycbcr_enc(&vsensor->tpg, format->ycbcr_enc);
 	tpg_s_quantization(&vsensor->tpg, format->quantization);
@@ -127,8 +129,7 @@ static void vimc_sensor_adjust_fmt(struct v4l2_mbus_framefmt *fmt)
 	fmt->height = clamp_t(u32, fmt->height, VIMC_FRAME_MIN_HEIGHT,
 			      VIMC_FRAME_MAX_HEIGHT) & ~1;
 
-	/* TODO: add support for V4L2_FIELD_ALTERNATE */
-	if (fmt->field == V4L2_FIELD_ANY || fmt->field == V4L2_FIELD_ALTERNATE)
+	if (fmt->field == V4L2_FIELD_ANY)
 		fmt->field = fmt_default.field;
 
 	vimc_colorimetry_clamp(fmt);
-- 
2.43.0