BSP and Device Driver Development Guide
All ATA driver functionality is available via ATA driver ioctl. Current implementation supports only two ioctls: BLKIO_REQUEST and ATAIO_SET_MULTIPLE_MODE. Each ATA driver ioctl() call generates an ATA request which is appended to the appropriate controller queue depending on ATA device the request belongs to. If appended request is single request in the controller's queue then ATA driver event is generated.
ATA driver task which manages queue of ATA driver events is core of ATA driver. In current driver version queue of ATA driver events implemented as RTEMS message queue. Each message contains event type, IDE controller minor number on which event happened and error if an error occurred. Events may be generated either by ATA driver ioctl call or by ATA driver task itself. Each time ATA driver task receives an event it gets controller minor number from event, takes first ATA request from controller queue and processes it depending on request and event types. An ATA request processing may also includes sending of several events. If ATA request processing is finished the ATA request is removed from the controller queue. Note, that in current implementation maximum one event per controller may be queued at any moment of the time.
(This part seems not very clear, hope I rewrite it soon)
BSP and Device Driver Development Guide
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