The cdpub Publisher

The cdpub device publisher retrieves and publishes information about CDs.

The publisher depends on the devb-eide CD driver. You may use a different driver on your system (for instance, devb-eide-mmx), but regardless of the hardware, the CD driver process runs continuously and manages the CD device path and communication with all CD device types, including DVDs, audio CDs, and CD-ROMs.

Architecture

Architectural diagram showing cdpub and the CD driver it uses to learn of disc insertions and to retrieve device information, which it publishes through PPS

Figure 1. CD publisher architecture

The arrows between components in Figure 1 show information flow. For example, when discs are inserted into or removed from the CD drive, the driver updates the state of the CD device object (/dev/cd0). That filesystem entry exists as long as the driver is running, even when the CD drive is empty.

The cdpub publisher also monitors the /dev entry (i.e., device object) and, when it notices a state change, asks the devb-eide process to obtain the latest device and mount information, which it then writes to the appropriate PPS objects. Subscribed applications receive PPS updates when CDs are inserted or removed.