Need help on device drivers

[hy71]

hi, I'm new in linux device drivers.
I wrote a drvier successfully compiled.
but some errors appeared when inserting, testing and removing modules.

Error messages are as below.

>>insmod myleddrv.ko
insmod: error inserting 'myleddrv.ko': -1 File exists
>>mknod /dev/myleddrv c 220 0
>>./mydrv_test.o (this is the test program)
test!
cannot open device!
: No such device or address
>>rmmod myleddrv
ERROR: Module myleddrv is in use

Could anybody help me on this? Thanks a lot.

[hy71]

the above problem is solved.
but , i'm facing another problem.

I can successfully insert the module and open this device by a test program.
However,when I try to remove this module, after typing "rmmod mydrv", the system got panic.
Would the reason of this problem be that other programs still are accessing its device file?
How to check before removing devices?

plz help me .
thanks for the info.

[Franklin52]

In /proc/modules there's a value that shows how many processes are using the module (3rd field).
If this number isn't zero, rmmod will fail.

Regards