now,, iam on programming the linux viosh,, for touchscreen system maybe its to hard for me...
So, how did you get roped into this project? This is not trivial stuff. If you don't know what you are doing, you are going to seriously harm your client. There are several areas of expertise you need to accomplish this:
1. Linux operating systems, kernels, and device drivers.
2. C and/or C++ programming.
3. User interface and HID (human interface device) integration with applications (the POS system).
If you aren't already competent on the first 2, I don't think you can accomplish #3 with any reasonable expectation of success. It is time for you to bring in people with the requisite experience and expertise.