ddcutil 2 slow on Acer XB271HU

[reticulatedpines]

Hi, first, thanks for ddcutil, it's a real time saver for me!

A recent system update, probably ddcutil going to v 2, has made an existing scripted command very slow. Previously, this was < 1s, now > 3s. Following some debugging advice in https://github.com/rockowitz/ddcutil/issues/110, I suspect related to dynamic sleep.

Abbreviated output showing some timing info:

$ /usr/bin/ddcutil --stats --bus 3 --sleep-multiplier=0.2 setvcp 10 + 10
Total non sleep system call time:        273 milliseconds
Total sleep call time:                  4398 milliseconds
Elapsed time:                           4722 milliseconds

$ /usr/bin/ddcutil --stats --bus 3 --disable-dynamic-sleep --sleep-multiplier=0.2 setvcp 10 + 10
Total non sleep system call time:        266 milliseconds
Total sleep call time:                   953 milliseconds
Elapsed time:                           1270 milliseconds

$ /usr/bin/ddcutil --stats --bus 3 --disable-dynamic-sleep --noverify --sleep-multiplier=0.2 setvcp 10 + 10
Total non sleep system call time:        267 milliseconds
Total sleep call time:                   953 milliseconds
Elapsed time:                           1271 milliseconds

$ /usr/bin/ddcutil --stats --bus 3 --skip-ddc-checks --sleep-multiplier=0.2 setvcp 10 + 10
Total non sleep system call time:         32 milliseconds
Total sleep call time:                   111 milliseconds
Elapsed time:                            186 milliseconds

$ /usr/bin/ddcutil --stats --bus 3 --skip-ddc-checks setvcp 10 + 10
Total non sleep system call time:         33 milliseconds
Total sleep call time:                   100 milliseconds
Elapsed time:                            176 milliseconds

Changing brightness seems very reliable with any of the above calls, I've not noticed it ever failing. This monitor has dubious DDC support, you must first put it in factory mode with the physical controls. So, don't feel you have to support it! If you'd like to try, please let me know if you want any additional info. If you just want to close this, that's fine by me.

I am an experienced C dev and should be able to do local builds of branches etc, if that's helpful.