Device Publishers
Device publishers are hardware-support components that publish information about attached devices. The QNX OS ships the usblauncher_otg publisher for USB-connected devices. This publisher sends information through its embedded resource manager publisher (RMPS) component. Applications use this information to access the content on devices, which allows them to display file information in browsers or to use multimedia services to read and play media files from those devices.
Applications could send commands to device drivers to read device information, but this design requires developers to learn hardware interfaces, which is inconvenient. Device publishers offer a reliable source of device information by allowing applications to subscribe to RMPS objects to receive device updates.
- its raw device name
- its mountpoint
- the names and indexes of its partitions
- connection information such as bus number, device number, and slot number
Device publishers don't monitor the physical connection of devices. Other system services monitor hardware events and respond when users attach or detach storage devices (such as USB sticks). For instance, the USB server monitors the USB hardware and reacts to each USB device attachment or detachment by notifying the usblauncher_otg service.
Device publishers run as persistent background processes. Typically, they're launched during bootup. You can restart publishers if they unexpectedly terminate.