USB Mouse detection

RichardS · 08-14-2007, 06:54 AM

Hi All,

I am currently playing with a USB mouse on an embedded version of Linux.

Is it possible to be notified when a USB mouse is plugged in?

The kernel has generic support for it, and I see some debug when the mouse is plugged in, but I was hoping for a more elegant solution than just polling the /dev/mouse device.

thanks,
Rich

ta0kira · 08-15-2007, 06:15 PM

Do you have udev set up? You can have it execute a command on a certain peripheral event. I use it to mount partitions and images when USB drives are plugged in. Look here: http://reactivated.net/writing_udev_rules.html
ta0kira

RichardS · 08-16-2007, 02:08 AM

Thanks. But I do not see how to udev. udev will create device nodes, but I am more looking for a coding solution. How do I detect the USB mouse within code, rather than getting a nice device node name?

mann3r · 08-16-2007, 05:25 AM

i want to know this one too, for my current project I am developing for manufacturing

ta0kira · 08-16-2007, 06:20 AM

In addition to creating a device, udev can execute a script. If you want your script to detect the connection rather than having it executed when the device is connected, have udev run a script that creates some indication that the device is connected which your script will check for. The same script can remove that indication when the device is no longer connected.
ta0kira

RichardS · 08-16-2007, 06:31 AM

Ok. But my programme is not a script. The only way I can think is that the script would send some sort of signal (e.g. SIGUSER1) and have the programme pickit up. Can scripts do this?

ta0kira · 08-16-2007, 08:00 AM

Yes. You need to know the PID or the name it's called under. With the PID do kill -s SIGUSR1 <pid> and with the script name do pkill -SIGUSR1 <name>. You must be careful to name the program something unique which won't be a part of something else's name. For example, "server" would be a good name to avoid.
ta0kira

ta0kira · 08-16-2007, 05:26 PM

A better way to go with pkill would be pkill -SIGUSR1 ^<name>$. That will force only full-name matches and will send the signal to all processes under that name. I use pkill/pgrep constantly and they are very useful. You should also really check out that udev site. It's more versatile than you think.
ta0kira