Where Does ddcutil Keep State?
ddcutil monitor state on Linux, detection cache plus user scripts for brightness.
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ddcutil talks DDC/CI to external monitors and keeps no config file of its own. Detection output and capability strings guide scripts. Buses renumber after cable changes.
Save detect output with your scripts as documentation. The durable part is user automation in shell or udev form. Keep monitor specific values beside the scripts.
Where ddcutil stores this, by platform
~/.config/ddcutil/ddcutilrc
No config file exists upstream. Cache detect output with scripts. I2C permissions gate access before any value changes.
Frequently asked questions
How do I script ddcutil brightness?
Run ddcutil detect and save the bus numbers per monitor. Script setvcp calls with those numbers. Re detect after cable swaps since buses move.
Why does ddcutil find no monitors?
Check I2C access rights and load i2c-dev. Laptops with internal panels often lack DDC entirely. External monitors over DisplayPort behave best.
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