[PATCH V2 2/2] media: video-i2c: append register data on MLX90640's frame

[Seongyong Park <euphoriccatface@gmail.com>]

On MLX90640, Each measurement step updates half of the pixels in the frame
(every other pixel in default "chess mode", and every other row
in "interleave mode"), while additional coefficient data (25th & 26th row)
updates every step. The compensational coefficient data only corresponds
with the pixels updated in the same step.

Only way to know which "subpage" was updated on the last step is to read
"status register" on address 0x8000. Without this data,
compensation calculation may be able to detect which sets of pixels have
been updated, but it will have to make assumptions when frame skip happens,
and there is no way to do it correctly when the host simply cannot
keep up with refresh rate.

Signed-off-by: Seongyong Park <euphoriccatface@gmail.com>
---
 drivers/media/i2c/video-i2c.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
index 2ccb08335..f2313b446 100644
--- a/drivers/media/i2c/video-i2c.c
+++ b/drivers/media/i2c/video-i2c.c
@@ -74,7 +74,8 @@ static const struct v4l2_fmtdesc mlx90640_format = {
 
 static const struct v4l2_frmsize_discrete mlx90640_size = {
 	.width = 32,
-	.height = 26, /* 24 lines of pixel data + 2 lines of processing data */
+	.height = 27,
+	/* 24 lines of pixel data + 2 lines of processing data + 1 line of registers */
 };
 
 static const struct regmap_config amg88xx_regmap_config = {
@@ -168,8 +169,12 @@ static int amg88xx_xfer(struct video_i2c_data *data, char *buf)
 
 static int mlx90640_xfer(struct video_i2c_data *data, char *buf)
 {
-	return regmap_bulk_read(data->regmap, 0x400, buf,
-				data->chip->buffer_size);
+	int ret = regmap_bulk_read(data->regmap, 0x400, buf,
+				   data->chip->buffer_size - 64);
+	if (ret)
+		return ret;
+	return regmap_bulk_read(data->regmap, 0x8000, buf + (data->chip->buffer_size - 64),
+				64);
 }
 
 static int amg88xx_setup(struct video_i2c_data *data)
@@ -375,7 +380,7 @@ static const struct video_i2c_chip video_i2c_chip[] = {
 		.format		= &mlx90640_format,
 		.frame_intervals	= mlx90640_frame_intervals,
 		.num_frame_intervals	= ARRAY_SIZE(mlx90640_frame_intervals),
-		.buffer_size	= 1664,
+		.buffer_size	= 1728,
 		.bpp		= 16,
 		.regmap_config	= &mlx90640_regmap_config,
 		.nvmem_config	= &mlx90640_nvram_config,
-- 
2.31.1