If the OP wants to take that road then the O'Reilly book Linux Device Drivers is available. The text is under a liberal open source licence, so you can read it online for free.

Another approach would be to create a FUSE filing system, and create an artificial block device or mountable file-system image inside.

Having said that, I doubt that the OP really needs to write a block device.

In reply to Re^2: imitation block device in linux by chrestomanci
in thread imitation block device in linux by butchie3980

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