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Currently we have the following algorithm to calculate what value should be
written to the exposure control of imx412.
lpfr = imx412->vblank + imx412->cur_mode->height;
shutter = lpfr - exposure;
The 'shutter' value is given to IMX412_REG_EXPOSURE_CIT however, the above
algorithm will result in the value given to IMX412_REG_EXPOSURE_CIT
decreasing as the requested exposure value from user-space goes up.
e.g.
[ 2255.713989] imx412 20-001a: Received exp 1608, analog gain 0
[ 2255.714002] imx412 20-001a: Set exp 1608, analog gain 0, shutter 1938, lpfr 3546
[ 2256.302770] imx412 20-001a: Received exp 2586, analog gain 100
[ 2256.302800] imx412 20-001a: Set exp 2586, analog gain 100, shutter 960, lpfr 3546
[ 2256.753755] imx412 20-001a: Received exp 3524, analog gain 110
[ 2256.753772] imx412 20-001a: Set exp 3524, analog gain 110, shutter 22, lpfr 3546
This behaviour results in the image having less exposure as the requested
exposure value from user-space increases.
Other sensor drivers such as ov5675, imx218, hid556 and others take the
requested exposure value and use the value directly.
Take the example of the above cited sensor drivers and directly apply the
requested exposure value from user-space. The 'lpfr' variable still
functions as before but the 'shutter' variable can be dispensed with as a
result.
Once done a similar run of the test application requesting higher exposure
looks like this, with 'exp' written directly to the sensor.
[ 133.207884] imx412 20-001a: Received exp 1608, analog gain 0
[ 133.207899] imx412 20-001a: Set exp 1608, analog gain 0, lpfr 3546
[ 133.905309] imx412 20-001a: Received exp 2844, analog gain 100
[ 133.905344] imx412 20-001a: Set exp 2844, analog gain 100, lpfr 3546
[ 134.241705] imx412 20-001a: Received exp 3524, analog gain 110
[ 134.241775] imx412 20-001a: Set exp 3524, analog gain 110, lpfr 3546
The result is then setting the sensor exposure to lower values results in
darker, less exposure images and vice versa with higher exposure values.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.