T-Kernel Specification (1.B0.02)

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240 CHAPTER 5. T-KERNEL/SM The function openfn performs processing to enable use of a device. Details of the processing are device-dependent; if no processing is needed, it does nothing. The device driver does not need to remember whether a device is open or not, nor is it necessary to treat as error the calling of another processing function simply because the device was not opened (openfn had not been called). If another processing function is called for a device that is not open, the necessary processing can be performed so long as there is no problem in device driver operation. When openfn is used to perform device initialization or the like, in principle no processing should be performed that causes a WAIT state. The processing and return from openfn must be as prompt as possible. In the case of a device such as a serial port for which it is necessary to set the communication mode, for example, the device can be initialized when the communication mode is set by tk wri dev. There is no need for openfn to initialize the device. When the same device is opened multiple times, normally this function is called only for the first time. If, however, the driver attribute TDA OPENREQ is designated in device registration, this function is called each time the device is opened. The openfn function does not need to perform any processing with regard to multiple opening or open mode, which are handled by device management. Likewise, omode is simply passed as reference information; no processing relating to omode is required. • Close Function: ER closefn( ID devid, UINT option, VP exinf ) devid option exinf return code Device ID of the device to close Close option (same as tk cls dev) Extended information set at device registration Error The close function closefn is called when tk cls dev is invoked. The closefn function performs processing to end use of a device. Details of the processing are device-dependent; if no processing is needed, it does nothing. If the device is capable of ejecting media and TD EJECT is set in option, media ejection is performed. When closefn is used to perform device shutdown processing or media ejection, in principle no processing should be performed that causes a WAIT state. The processing and return from closefn must be as prompt as possible. If media ejection takes time, it is permissible to return from closefn without waiting for the ejection to complete. When the same device is opened multiple times, normally this function is called only the last time it is closed. If, however, the driver attribute TDA OPENREQ is designated in device registration, this function is called each time the device is closed. In this case TDA EJECT is designated in option only for the last time. The closefn function does not need to perform any processing with regard to multiple opening or open mode, which are handled by device management. • Processing Start Function: ER execfn( T_DEVREQ *devreq, TMO tmout, VP exinf ) devreq tmout exinf return code Request packet Request acceptance timeout (ms) Extended information set at device registration Error The execfn function is called when tk rea dev or tk wri dev is invoked, and starts the processing requested in devreq. This function starts the requested processing only, returning to its caller Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
5.3. DEVICE MANAGEMENT FUNCTIONS 241 without waiting for the processing to complete. The time required to start processing depends on the device driver; this function does not necessarily complete immediately. When new processing cannot be accepted, this function goes to WAIT state for request acceptance. If the new request cannot be accepted within the time designated in tmout, the function times out. The attribute TMO POL or TMO FEVR can be designated in tmout. If the function times out, E TMOUT is passed in the execfn return code. Timeout applies to the request acceptance, not to the processing after acceptance. When error is passed in the execfn return code, the request is considered not to have been accepted and the request packet is discarded. If processing is aborted before the request is accepted (before the requested processing starts), E ABORT is passed in the execfn return code and the request packet is discarded. If the abort occurs after the processing has been accepted, E OK is returned for this function. The request packet is not discarded until waitfn is executed and processing completes. When abort occurs, the important thing is to return from execfn as quickly as possible. processing will end soon anyway without aborting, it is not necessary to abort. • Completion Wait Function: INT waitfn( T_DEVREQ *devreq, INT nreq, TMO tmout, VP exinf ) devreq nreq tmout exinf return code Request packet list Request packet count Timeout designation (ms) Extended information set at device registration Completed request packet number or error The waitfn function is called when tk wai dev is invoked. devreq is a list of request packets in a chain linked by devreq->next. This function waits for completion of any of the nreq request packets starting from devreq. The final next is not necessarily NULL, so the nreq designation must always be followed. The number of the completed request packet (which one after devreq) is passed in the return code. The first one is numbered 0 and the last one is numbered nreq − 1. Here completion means any of normal completion, abnormal (error) termination, or abort. The time to wait until completion is set in tmout. TMO POL or TMO FEVR can be designated as the tmout attribute. If the wait times out, the requested processing continues. The waitfn return code in case of timeout is E TMOUT. The request packet error parameter does not change. Note that if return from waitfn occurs while the requested processing continues, error must be returned in the waitfn return code; but the processing must be completed even when error is passed in the return code, and a value other than error must not be returned if processing is ongoing. As long as error is not passed in the waitfn return code, the request is considered to be pending and no request packet is discarded. When the number of a request packet whose processing was completed is passed in the waitfn return code, the processing of that request is considered to be completed and that request packet is discarded. IO error and other device-related errors are stored in the request packet error parameter. Error is passed in the waitfn return code when completion waiting did not take place properly. The waitfn return code is set in the tk wai dev return code, whereas the request packet error value is returned in ioer. Abort processing differs depending on whether the wait is for completion of a single request (nreq = 1) or multiple requests (nreq > 1). When completion of a single request is being waited for, the request currently processing is aborted. When waiting for completion of multiple requests, If Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
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T-Kernel Specification T-Kernel 1.B
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Contents 1 T-Kernel Overview 1 1.1
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CONTENTS v tk set flg (Set Event Fl
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CONTENTS vii 5.2.2 Address Space Ch
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CONTENTS ix td cal que (Reference Q
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List of Figures 1.1 Position of T-K
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List of Tables 2.1 State Transition
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System Call Notation In the parts o
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Index of T-Kernel/OS System Calls T
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INDEX OF T-KERNEL/OS SYSTEM CALLS x
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Index of T-Kernel/SM Extended SVC L
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Index of T-Kernel/DS System Calls T
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Chapter 1 T-Kernel Overview 1.1 Pos
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1.2. SCALABILITY 3 • Middleware m
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Chapter 2 Concepts Underlying the T
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2.2. TASK STATES AND SCHEDULING RUL
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2.2. TASK STATES AND SCHEDULING RUL
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2.3. INTERRUPT HANDLING 11 preceden
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2.5. SYSTEM STATES 13 Transient sta
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2.7. MEMORY 15 which the upper and
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Chapter 3 Common T-Kernel Specifica
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3.2. SYSTEM CALLS 19 /* * Common co
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3.2. SYSTEM CALLS 21 Ordinarily a f
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3.3. HIGH-LEVEL LANGUAGE SUPPORT RO
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Chapter 4 T-Kernel/OS Functions Thi
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4.1. TASK MANAGEMENT FUNCTIONS 27 t
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4.7. TIME MANAGEMENT FUNCTIONS 163
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4.8. INTERRUPT MANAGEMENT FUNCTIONS
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290 CHAPTER 7. REFERENCE E OACV ERC
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T-Kernel Specification (1.B0.02)

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