Hello everyone.
I have been looking at ways to do runtime devicetree overlay
application, and was just wondering what the current status of the
different proposals [0], [1] were. They seem to be quite old and I think
they were already rejected, but due to all the broken links, I am not
really sure about the exact reasons. Also, maybe we now have the
solutions to some the blockers at the time.
Let me fist go over some of the use cases where I think dynamic
devicetree overlays can be useful. I am mostly interested in their use
in single board computers like PocketBeagle 2 [2], Raspberry Pi [3], etc.
# Uses
## Dynamic Pin muxing
A lot of SBC's aimed for creating hardware projects expose headers,
where each pin can be used for multiple things like GPIO, I2C, PWM, etc,
depending on the pinmux. I think Raspberry Pi has it's own solution to
do userspace pinmux, but if userspace devicetree application was a
thing, it could probably be used for this. Additionally, being able to
use dynamic devicetree overlays for pin muxing would allow much easier
transition to use proper device trees during production.
## Dynamic Sensors/Devices
Using devices such as sensors, external ADCs, EEPROMs, etc are also a
common usecase in SBC's. A lot of current solutions seem to be designed
around using user-space drivers in such cases. This is a bit of a shame
since Linux kernel already has drivers for a lot of these drivers, and
they are probably going to be of higher quality than most user space
drivers.
# Challenges
## Security
The concerns regarding security seemed to show up in the other
proposals. There was a proposal to have a devicetree property to
allow/deny the application of overlays in some nodes, with default being
deny. Was it insufficient?
## Memory Leaks
Currently, updating/removing properties leaks memory. Was it one of the
reasons for the rejection of previous proposals?
Maybe kernel already has some solutions more suited to my usecase that I
am unware of?
[0]:
https://lore.kernel.org/all/1417605808-23327-1-git-send-email-pantelis.antoniou@xxxxxxxxxxxx/#t
[1]: https://lore.kernel.org/all/20161220190455.25115-1-xypron.glpk@xxxxxx/
[2]: https://www.beagleboard.org/boards/pocketbeagle-2
[3]: https://www.raspberrypi.com/
Best Regards,
Ayush Singh
