[PATCH 2/3] media: i2c: ov5675: Add OVTI5678 ACPI id

[Sahan Nissanka]

The front camera of the Dell Latitude 7320 Detachable is described in
ACPI as OVTI5678, and no driver has ever claimed that id. It reports
chip id 0x005675 at register 0x300a, which is what
ov5675_identify_module() expects, and it streams with this driver
unmodified:

  ov5675 i2c-OVTI5678:00: chip id at 0x300a reads 0x005675
    reg 0x300a = 0x00  reg 0x300b = 0x56  reg 0x300c = 0x75

The two other values this driver is sensitive to were read from the
machine's ACPI SSDB before the sensor was ever powered, and both agree:
L0NL = 2 data lanes (OV5675_DATA_LANES) and L0CK = 19200000 Hz
(OV5675_XVCLK_19_2). Native resolution matches at 2592x1944.

With this id added the sensor binds and streams: libcamera lists it and
capture runs at 2584x1944, 29.95 fps.

This part is not a plain Bayer sensor, however, and the format this
driver declares for it is inaccurate. It carries a 4x4 RGB-IR colour
filter array, one pixel in four being infrared:

    G I G I
    R G B G
    G I G I
    B G R G

Confirmed three ways. Intel's Windows IPU6 configuration for this exact
module - matched by ACPI _DDN, so not a near relative - declares
bayer_order="GIGI_RGBG_GIGI_BGRG" and sensor_type="RGB_IR". Measured on
the sensor at full resolution, positions a 2x2 model treats as a single
channel differ by 18% while the four infrared positions agree to 0.4%.
And the module's Intel tuning data carries a 4x4 channel index map that
agrees with both.

Read as the SGRBG10 declared here, the "blue" channel is pure infrared
and the "red" channel interleaves real red with real blue, so colour is
wrong in a way no white balance can correct.

This cannot be fixed in this driver: there is no RGB-IR media bus code
in the V4L2 ABI. Nor is it unique to this part - ox05b1s declares
SGRBG10 for an RGB-IR sensor of the same class and resolution. I intend
to propose RGB-IR media bus codes separately. Until such support
exists, this patch makes otherwise unusable hardware work, carrying the
same known inaccuracy as the existing RGB-IR sensor support.

One further note for anyone building on this: the sensor's binned
1296x972 mode averages infrared pixels together with colour ones, which
destroys the mosaic. Only the full resolution mode is meaningful for an
RGB-IR aware pipeline.

Signed-off-by: Sahan Nissanka <adee.sahan@xxxxxxxxx>
---
 drivers/media/i2c/ov5675.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/media/i2c/ov5675.c b/drivers/media/i2c/ov5675.c
index ea26df3..99dbf53 100644
--- a/drivers/media/i2c/ov5675.c
+++ b/drivers/media/i2c/ov5675.c
@@ -1355,6 +1355,17 @@ static const struct dev_pm_ops ov5675_pm_ops = {
 #ifdef CONFIG_ACPI
 static const struct acpi_device_id ov5675_acpi_ids[] = {
 	{"OVTI5675"},
+	/*
+	 * The front sensor of the Dell Latitude 7320 Detachable is described
+	 * as OVTI5678 in ACPI, but the part reports chip id 0x005675 and its
+	 * SSDB agrees with this driver on both other values that matter:
+	 * 2 CSI-2 data lanes and a 19.2 MHz external clock.
+	 *
+	 * Note this variant carries a 4x4 RGB-IR colour filter array, not the
+	 * 2x2 Bayer declared here, so colour is incorrect. There is currently
+	 * no RGB-IR media bus code to declare instead.
+	 */
+	{"OVTI5678"},
 	{}
 };
 
-- 
2.53.0