Changes between Version 14 and Version 15 of ioc_device_api
- Timestamp:
- Jan 21, 2020, 9:11:40 PM (5 years ago)
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ioc_device_api
v14 v15 11 11 The ''user'' API contains the functions used by the user-level system calls, and defines four operation types : the '''IOC_READ''', '''IOC_WRITE''', '''IOC_SYNC_READ''', and '''IOC_SYNC_WRITE''' operations move a given number of contiguous blocks between the block device and a kernel memory buffer. This API is detailed in section C below. 12 12 13 * The '''asynchronous''' READ and WRITE operations are not directly executed by the client thread. The READ and WRITE requests are registered in the waiting queue rooted in the IOC chdev descriptor. These requests are actually handled by a dedicated server thread running in the cluster containing the chdev descriptor, that call the ''ioc_driver_cmd()'' function.13 * The '''asynchronous''' READ and WRITE operations are not directly executed by the client thread. The READ and WRITE requests are registered in the waiting queue rooted in the IOC chdev descriptor. These requests are actually handled by a dedicated server thread running in the cluster containing the chdev descriptor, that calls the ''ioc_driver_cmd()'' function. 14 14 15 15 * The '''synchronous''' SYNC_READ and SYNC_WRITE operations does not use the waiting queue, and does not use the server thread. The client thread calls directly the ''ioc_driver_cmd()'' function. 16 16 17 Most IOC device implementation have a DMA capability, and the data transfer is not done by the software, but is actually done by the hardware device. The IOC IRQ signaling the transfer completion is routed to the core executing the server thread, and handled by the 18 ''ioc_driver_isr()'' function (ISR stand for Interrupt Service Routine). 17 Most IOC device hardware implementations have a DMA capability, and the data transfer is not done by the software, but is actually done by the hardware device. In this case, the IOC_IRQ signaling the transfer completion is routed to the core executing the server thread, and handled by the ''ioc_driver_isr()'' function (ISR stand for Interrupt Service Routine). 19 18 20 In the IOC-RDK implementation the IOCblock device is actually implemented as physical memory. This IOC-RDK implementation does not use DMA, and does not use an IRQ. The data transfer is directly executed by the ''ioc_driver_cmd()'' software function.19 An exception is the IOC-RDK implementation, where the block device is actually implemented as physical memory. This IOC-RDK implementation does not use DMA, and does not use an IRQ. The data transfer is directly executed by the ''ioc_driver_cmd()'' software function. 21 20 22 21 To access the various drivers, the IOC device defines a lower-level ''driver'' API, that is detailed in section D below. … … 35 34 36 35 == __C) User API__ == 37 38 39 36 40 37 These four I/O operations are blocking for the calling thread, but the blocking policy depends on the operation type.
