hi,
i have written a character driver..i have done trimming in open call...when i run an application i do like follows
[char_driver]# make
[char_driver]# insmod ./modules/lkm.c
[char_driver]# gcc app.c //my appliaction
[char_driver]# mknod node c 250 0
[char_driver]# ./a.out node
........it works fine......
however if i make another node i.e after instruction
[char_driver]# mknod node c 250 0
i type
[char_driver]# mknod node1 c 250 0
and then
[char_driver]# ./a.out node
it works
and if i type
[char_driver]# ./a.out node1
it crashes
please help....
i think it is trimming problem.....plz tell where to trim in read or open....
regards
zaffer

You can not have two devices with the same minor number, if you want to handle two devices from your driver make sure your driver is registered to handle two devices and you create the devices with different minor numbers.

thanks dear.....can u tell me how can we have two different minor numbers......wat i think is that we have use two character devices with two minor nos e.g mknod node c 250 0 ,mknod node1 c 250 1.......like that

Yes that is how you give two different minor numbers.
your driver should also be registered to handle two devices and there should be separate cdev structures to handle the devices.