FLASH savings feature tracker

[dakejahl]

I am creating this issue so that we can keep track of a list of options for reducing FLASH usage throughout the project. Please feel free to edit this description to update the list.

• Split builds by airframe type
• Compile time airframe selection (eg /etc/init.d/airframes/4050_generic_250)
• Compile time rcS and compile time module start hooks
• Selectively compile mavlink messages/features (context here [mavlink] KConfig for minimal functionality (flash savings) #22930)
• Split GNSS drivers by module type (kill gps.cpp monolith)
• Reduce strings (log using events, reduce the number of PX4_INFO calls, also analyze why we have > 100K of string data)
• Don't include longDesc in parameter description
• Store/update px4io FW on SD card instead of ROMFS
• Refactor invsense IMU drivers, they share a lot of common code

@alexcekay @dagar

[DronecodeBot]

This issue has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-dev-call-aug-27-2025-team-sync-and-community-q-a/47194/1

[dagar]

I would argue that splitting things along vehicle type boundaries or breaking up monolithic drivers/modules is important architecturally for a variety of reasons, but I'd be perfectly content if pursuing flash savings is what motivates it.

We need to be more realistic about what actually should be runtime configurable and even more importantly I think we need to structure the system so that it enables all these disparate groups to develop rapidly without stomping on each other (or forking and never looking back).

[dirksavage88]

@dakejahl is there a way to profile where the majority of flash usage is coming from? For example on the v6x. I am wondering if it is worth also going down to the common x (driver level) and disabling some of these lesser used drivers. Also taking a granular look at each driver and seeing if any flash savings could be had. Similar to what was done for the common code across the IMU drivers, but applied to peripheral sensors.

[alexcekay]

@dirksavage88: I created this just a few days ago. https://docs.google.com/spreadsheets/d/1Gh-S_VSWtpxTG43m1hhNQfr3SG523hlGoGV1z8SUOt0/edit?usp=sharing

Can share the tooling if you guys are interested.

[dakejahl]

bloaty for flash profiling
https://github.com/google/bloaty
https://docs.px4.io/main/en/debug/binary_size_profiling.html

[DronecodeBot]

This issue has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-dev-call-sep-3-2025-team-sync-and-community-q-a/47287/1