What is my i2c device slave address?

I am recently porting an i2c touchscreen to my board which runs ARM linux 3.1. I found I need to setup some device platform data for the i2c chip, among which there is an 'addr' field that I dont understand. I search the device driver code, then I know the address will be used when compositing some i2c messages. My question is that how do I know what the address I should fill in the field? The datasheet of the device doesn't provide an answer. By the way, the touchscreen is actually an Atmel mXT224 i2c multi-touch screen panel, which is wired to a Samsung S3C i2c controller in my SoC. Thanks in advance! -woody -- Sent from Gmail Mobile