I'm trying to add an overlay for Sony pdx213 (xperia 10 III), and could use a few pointers about vendor_hardware_overlay HOT 3 CLOSED

from vendor_hardware_overlay.

I get your frustrations buddy, I've been there before. Being such a niche product family, little resource and community can be found for this device, making further development somewhat tricky. Sony is kind enough to provide the SODP repos but I couldn't find too much useful config out of it (you could probably make use of power_config.xml but I wasn't able to see the difference before and after applying it).
Anyways I searched around and was able to get in touch with a previous maintainer of the device who shared his version of the device tree, which took a lot of testing and porting to create (it was initially a fork of the device tree for a Oneplus device and I believe they tested out the appropriate configurations for the current device). I used the values in that tree and made the overlay. A lot of other config items were applied but wasn't necessary for auto-brightness.
Unfortunately I searched Github and had no luck finding a existing open device tree repo for pdx213 (except for the one by Sony) which means you'll have to either make your own tree or try to find existing but private ones. I see Sjll (on xda and github) has been releasing roms for pdx213, see if you can contact him and get some help.
Another choice that sits somewhere in the middle is to find existing configs for device with similiar display panel (I doubt there's any device with the exact same panel) or its siblings (maybe even start with values from my overlay) and tweak it to an appropriate set. This could involve a lot of flashing and testing so be prepared.
As for unpacking Sony roms, you can easily see the partitions in .sin files and you need to further unpack those. Go search for a tool named UnSin on xda and follow the guide there. You'll probably need more tools such as lpunpack, ext2rd, etc, depending on which partiton you want to check out. I was able to extract framework-res.apk from system partition but found no configs related to brightness values so good luck with that.

from vendor_hardware_overlay.

I have indeed found that unsin will allow me to mount the firmware image, but as you said it only seems to contain the power config and not the config file that controls the stuff of interest like auto brightness.

At first glance it looks like Sony also did not provide the relevant config on their github but ada12 pointed out that the bulk of the config lives in https://github.com/sonyxperiadev/device-sony-common/blob/master/overlay/frameworks/base/core/res/res/values/config.xml with only device-specific extension in https://github.com/sonyxperiadev/device-sony-pdx213/blob/master/overlay/frameworks/base/core/res/res/values/config.xml so that's the route I'm trying to take. Let's see if it actually works.

Current progress is in #413

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