Logitech optical mouse scroll wheel not working correctly

Some more investigation pinpointed the problem to the kernel, not the X mouse driver.

In kernel 2.6.17 (which I had in 6.10), dmesg lines related to the mouse were
[17179572.484000] mice: PS/2 mouse device common for all mice
[17179592.040000] logips2pp: Detected unknown logitech mouse model 56
[17179592.568000] input: ImExPS/2 Logitech Explorer Mouse as /class/input/input2

"cat /sys/class/input/mouse0/device/protocol" shows the protocol as "ImExPS/2".

In kernel 2.6.20, I get these instead:
[ 18.320140] mice: PS/2 mouse device common for all mice
[ 18.320606] input: Macintosh mouse button emulation as /class/input/input0
[ 40.291729] input: PS/2 Logitech Wheel Mouse as /class/input/input3

"cat /sys/class/input/mouse0/device/protocol" shows the protocol as "PS/2"
(This despite model 56 supposedly being recognized by the driver since commit e3882bb56e31dbb3950e51c1ba914ef2f445650c)

Unfortunately I won't have time in the near future to bisect this... Hopefully in a few weeks. Meanwhile I will be using kernel 2.6.17.
(Are there instructions anywhere for bisecting kernel bugs in an Ubuntu system? Specifically, how do I run with a custom-built kernel?)

Beginning with the Hardy Heron 8.04 development cycle, all open Ubuntu kernel bugs need to be reported against the "linux" kernel package. We are automatically migrating this bug to the new "linux" package. However, development has already began for the upcoming Intrepid Ibex 8.10 release. It would be helpful if you could test the upcoming release and verify if this is still an issue - http://www.ubuntu.com/testing . If the issue still exists, please update this report by changing the Status of the "linux" task from "Incomplete" to "New". We appreciate your patience and understanding as we make this transition. Thanks!

This was fixed in 2.6.23 (commit 554fc1935365ddba0936dfb6dc4088ba4ef23a4f)

The Ubuntu Kernel Team is planning to move to the 2.6.27 kernel for the upcoming Intrepid Ibex 8.10 release. As a result, the kernel team would appreciate it if you could please test this newer 2.6.27 Ubuntu kernel. There are one of two ways you should be able to test:

1) If you are comfortable installing packages on your own, the linux-image-2.6.27-* package is currently available for you to install and test.

--or--

2) The upcoming Alpha5 for Intrepid Ibex 8.10 will contain this newer 2.6.27 Ubuntu kernel. Alpha5 is set to be released Thursday Sept 4. Please watch http://www.ubuntu.com/testing for Alpha5 to be announced. You should then be able to test via a LiveCD.

Please let us know immediately if this newer 2.6.27 kernel resolves the bug reported here or if the issue remains. More importantly, please open a new bug report for each new bug/regression introduced by the 2.6.27 kernel and tag the bug report with 'linux-2.6.27'. Also, please specifically note if the issue does or does not appear in the 2.6.26 kernel. Thanks again, we really appreicate your help and feedback.

This bug report is being closed due to your last comment regarding this being fixed with an update. For future reference you can manage the status of your own bugs by clicking on the current status in the yellow line and then choosing a new status in the revealed drop down box. You can learn more about bug statuses at https://wiki.ubuntu.com/Bugs/Status . Thank you again for taking the time to report this bug and helping to make Ubuntu better. Feel free to submit any future bugs you may find.