Comment 17 for bug 377175

I see two possibilities why the Macally keyboard locks the screen. Either it emits Usage ID 0xF9 on HID Usage Page 0x07 (Keyboard), or it emits Usage ID 0x19e on HID Usage Page 0x0C (Consumer). In order to verify this theory, it might be useful to have a look at the HID descriptor and the HID events.

Depending on the results, special quirk handling of the keyboard might be added to the linux kernel and/or gnome-screensaver gets a option to ignore the (fake) "lock screen" key.

HOWTO:
1. get the USB vendor+product ID using lsusb
> lsusb
Search for the line with the Macally Keyboard
(e.g. I get "Bus 001 Device 007: ID 046a:0023 Cherry GmbH CyMotion Master Linux Keyboard" for my keyboard, so the vendor:id is 046a:0023)

2. look at the device descriptors
> cd /sys/kernel/debug/hid
> ls
(I have here four entries, my keyboard makes up two of them 0003:046A:0023.0002 and 0003:046A:0023.0003; notice the matching vendor:id 046a:0023)
> sudo cat $YOUR_DEVICE1/rdesc
> sudo cat $YOUR_DEVICE2/rdesc

3. look at the events of the keys
(Please be aware that the following records all your keypresses, so don't enter passwords or other sensitive information if you intend to post the event log to the bug report! Entering the password for "sudo" is ok, because it asks the password _before_ running the command)
3.1 first device
> sudo cat $YOUR_DEVICE1/events
press the volume up key
exit with CTRL-C
3.2 second device
> sudo cat $YOUR_DEVICE2/events
press the volume up key again
exit with CTRL-C

Please find attached the output from my keyboard. It is only for demonstration purposes, because when connected via USB my keyboard does not exhibit the "lock screen" bug.