T-Kernel Specification (1.B0.02)

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232 CHAPTER 5. T-KERNEL/SM The time required for write start processing differs with the device; return of control is not necessarily immediate. In the case of device-specific data, the start and size units are decided for each device. With attribute data, start is an attribute data number and size is in bytes. The attribute data of the data number designated in start is written. Normally size must be at least as large as the size of the attribute data to be written. Multiple attribute data cannot be written in one operation. When size = 0 is designated, actual writing does not take place but the current size of data that can be written is checked. Whether or not a new request can be accepted while a read or write operation is in progress depends on the device driver. If a new request cannot be accepted, the request is queued. The timeout for request waiting is set in tmout. The TMO POL or TMO FEVR attribute can be designated for tmout. Note that what times out is request acceptance. Once a request has been accepted, this function does not time out. E ID E OACV E RONLY E LIMIT E TMOUT E ABORT Other dd is invalid or not open Open mode is invalid (write not permitted) Read-only device Number of requests exceeds the limit Busy processing other requests Processing aborted Errors returned by device driver • ER tk_swri_dev( ID dd, INT start, VP buf, INT size, INT *asize ) Synchronous write. This is equivalent to the following. ER tk_swri_dev( ID dd, INT start, VP buf, INT size, INT *asize ) { ER er, ioer; er = tk_wri_dev(dd, start, buf, size, TMO_FEVR); if ( er > 0 ) { er = tk_wai_dev(dd, er, asize, &ioer, TMO_FEVR); if ( er > 0 ) er = ioer; } return er; } • ID tk_wai_dev( ID dd, ID reqid, INT *asize, ER *ioer, TMO tmout ) dd reqid asize ioer tmout return code Device descriptor Request ID Returns the read/write data size Returns IO error Timeout (ms) Completed request ID or error Waits for completion of request reqid for device dd. If reqid = 0 is set, this function waits for completion of any pending request to dd. This function waits for completion only of requests currently processing when the function is called. A request issued after tk wai dev was called is not waited for. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
5.3. DEVICE MANAGEMENT FUNCTIONS 233 When multiple requests are being processed concurrently, the order of their completion is not necessarily the same as the order of request but is dependent on the device driver. Processing is, however, guaranteed to be performed in a sequence such that the result is consistent with the order of requesting. When processing a read operation from a disk, for example, the sequence might be changed as follows. Block number request sequence 1 4 3 2 5 Block number processing sequence 1 2 3 4 5 Disk access can be made more efficient by changing the sequence as above with the aim of reducing seek time and spin wait time. The timeout for waiting for completion is set in tmout. The TMO POL or TMO FEVR attribute can be designated for tmout. If a timeout error is returned (E TMOUT), tk wai dev must be called again to wait for completion, since the request processing is ongoing. When reqid > 0 and tmout = TMO FEVR are both set, the processing must be completed without timing out. If the requested processing results in error (IO error, etc.) ioer is stored rather than a return code. The return code is used for errors when the request wait itself was not handled properly. When error is passed in the return code, ioer has no meaning. Note also that if error is passed in the return code, tk wai dev must be called again to wait for completion, since the request processing is ongoing. If a task exception is raised during completion waiting by tk wai dev, the request in reqid is aborted and processing is completed. The result of aborting the requested processing is dependent on the device driver. When reqid = 0 was set, however, requests are not aborted but are treated as timeout. In this case E ABORT rather than E TMOUT is returned. It is not possible for multiple tasks to wait for completion of the same request ID at the same time. If there is a task waiting for request completion with reqid = 0 set, another task cannot wait for completion for the same device descriptor. Similarly, if there is a task waiting for request completion with reqid > 0 set, another task cannot wait for completion designating reqid = 0. E ID dd is invalid or not open reqid is invalid or not a request for dd E OBJ Another task is already waiting for request reqid E NOEXS No requests are being processed (only when reqid = 0) E TMOUT Timeout (processing continues) E ABORT Processing aborted Other Errors returned by device driver • INT tk_sus_dev( UINT mode ) mode return code Mode Suspend disable request count or error Performs the processing designated in mode, then passes the resulting suspend disable request count in the return code. mode := ( (TD_SUSPEND | [TD_FORCE]) || TD_DISSUS || TD_ENASUS || TD_CHECK) #define TD_SUSPEND 0x0001 /* suspend */ 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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Page 205 and 206: 4.7. TIME MANAGEMENT FUNCTIONS 181
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282 CHAPTER 6. T-KERNEL/DS FUNCTION
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284 CHAPTER 7. REFERENCE INT tevptn
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286 CHAPTER 7. REFERENCE ER ercd =
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288 CHAPTER 7. REFERENCE INT ct = t
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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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