After "re"-plugin USB mouse, can't reopen it

[heikifm]

Hi all!
I'm programming USB mouse api on my embedded linux system.

To read mouse event, I typed "mknod /dev/input/event0 c 13 64" and
opened it to read.

After checking correct ouput from that, plugged out usb mouse.

And "cat /dev/input/event0", prints "no such device". It's ok.

But after re-plugin mouse, I can't read() /dev/input/event0 .

On prompt typping "cat /dev/input/event0", still prints "no such device"
even though mouse is being connected.

So I close()ed "dev/input/event0" when unplug mouse, and re-open()ed it when plugin mouse, it is still not possible to open and read..

(and in "/proc/bus/input/devices", handler "event*" number increases,
when I open "dev/input/event*" and replugin mouse.)

What is the problem?

How can I re-open(or re-read) "/dev/input/event0" successfully
when replugin-ing mouse?

[i92guboj]

Hi all!
I'm programming USB mouse api on my embedded linux system.

To read mouse event, I typed "mknod /dev/input/event0 c 13 64" and
opened it to read.

After checking correct ouput from that, plugged out usb mouse.

And "cat /dev/input/event0", prints "no such device". It's ok.

But after re-plugin mouse, I can't read() /dev/input/event0 .

On prompt typping "cat /dev/input/event0", still prints "no such device"
even though mouse is being connected.

Right.

(and in "/proc/bus/input/devices", handler "event*" number increases,
when I open "dev/input/event*" and replugin mouse.)

What is the problem?

As far as I know, this is the way it work. If you want to make sure that a given device is always linked to the same device node, then you have to do some magic yourself. It's much easier if you use udev on that system, because a simple udev rule can do that for you:

Writing udev rules

You can match the device using any info that's unique to it.

I think that that should help.

[heikifm]

Thanks i92guboj,
Your advice is very helpful for me
I'll see udev part. Thank you.