imx290 : implement HCG/LCG mode

[gechdcb]

1. Allow switch the HCG/LCG mode at runtime via module parameter.
2. Add an optional dtoverlay parameter to set the max gain as the maximum analogue gain of the imx290 and imx327 is slightly different

[6by9]

Thanks for the PR.

The changes adding HCG mode are fine, however as this is a mainline Linux driver, we do ask that all commits follow the Linux coding standards. There's an automatic coding style checker in scripts/checkpatch.pl. For media subsystem patches you need to run it with --strict.

No codespell typos will be found - file '/usr/share/codespell/dictionary.txt': No such file or directory
WARNING: Missing commit description - Add an appropriate one

ERROR: do not initialise statics to false
#25: FILE: drivers/media/i2c/imx290.c:71:
+static bool hcgmode = false;

CHECK: Alignment should match open parenthesis
#76: FILE: drivers/media/i2c/imx290.c:1348:
+		ret = fwnode_property_read_u8(dev_fwnode(dev), "max-gain",
+									&max_gain);

ERROR: Missing Signed-off-by: line(s)

Commit message title should start with media: i2c: imx290: , and needs the signed off by (use git commit -s as the simple way to add it). One change per commit, so adding LCG/HCG control is separate from maximum gain.

The change to maximum gain is moot - IMX327 supports 29.4dB in 0.3dB steps for max 98, vs IMX290 supporting 30dB in 0.3dB steps for a max of 100. Digital gain is on the same register, so 100 on IMX327 you'll get 29.4dB of analogue gain and 0.6dB of digital gain, which is close enough in my book.

If you really want to distinguish between the two, then do so by adding an extra compatible string and adjusting the gain range based on that, not by creating a non-standard (and un-documented) device tree property.