I have a doubt regarding the device driver architecture. Some device drivers use the adi_dev_xxx set of functions whereas some of the drivers have the adi_pdd_xxx set. What is the difference. As far as I understand, both the function types have the same architecture (parameters, return types etc.). Also, pdd refers to the "physical device" which is also referred in the device driver and system services manual. Am I missing something? Please clarify.