How DVDROM device is identified

For some reason and thanks to Dell’s incorrect info, the firmware upgrade crashed.

Can anybody tell me the process of how BIOS identifies the DVD drive ?

I am more talking about a software solution - using tools like dos debug.exe. How can I read the raw IDE port ? I can do that for IDE harddisk using debug.exe esp by booting DOS.

I am looking to bpass BIOS if I can directly read/talk to the device.

Any help will be great. I dont mind writing something in C++

Thanks

Which drive do you have?

I have a TSST 632D - though I think my question doesnt change with the make of the drive.

Any clue to where I can get the info will be appreciated.

Thanks