JP2004145675A - Data input/output device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce overhead caused by a data transfer request of incorrect length. <P>SOLUTION: The practical data transfer length of data stored in a data buffer 13 is detected, data transfer length commanded from a master device 20 is compared with the practical data transfer length and the data transfer length of smaller length is set in an SCSI interface 11 to perform data transfer processing. Even when data length of incorrect length that the data transfer length specified from the master device 20 is longer than the practical data transfer length of data stored in the data buffer 13 is performed, the data transfer processing of the SCSI interface 11 is normally ended without forcedly interrupting the processing, so that the transfer of a forced end command, a forced end completion signal, a reset command, a reset end signal and the interruption control of data transfer processing in the SCSI interface 11 which are required for conventional incorrect length data transfer are unnecessitated, overhead is reduced and the efficiency and stabilization of the data transfer processing are improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention improves the data input / output device for performing data transfer between a higher-level device and a storage device, and more specifically, improves the efficiency and stability of transfer processing by reducing the overhead generated during data transfer. It relates to improvement to achieve.
[0002]
[Prior art]
2. Description of the Related Art There is known a data input / output device configured to transfer data between a host device and a storage device via a data buffer.
[0003]
FIG. 3 is a functional block diagram showing a general example of a conventional data input / output device provided between a host device and a storage device in SCSI.
[0004]
The data input / output device 10 generally includes a SCSI interface 11 (upper device interface) connected to the upper device 20, a drive interface 12 (lower device interface) connected to the storage device 30, and the SCSI interface 11. It comprises a data buffer 13 for temporarily storing data when exchanging data with the drive interface 12, and an input / output control means 14 for controlling the SCSI interface 11 and the drive interface 12.
[0005]
The input / output control means 14 sets the data transfer length specified by the read command from the host device 20 to the SCSI interface 11 and outputs a data transfer command to the SCSI interface 11. 13 is read via the illegal length detecting means 15, and the data is transferred to the host device 20.
[0006]
Here, if the data transfer length specified by the read command from the higher-level device 20 is equal to or smaller than the substantial data transfer length of the data stored in the data buffer 13, the SCSI interface 11 is set. Since the data having the same transfer length can be read from the data buffer 13 and transferred to the host device 20, the data transfer processing in the SCSI interface 11 ends normally, and the data is transferred from the SCSI interface 11 to the input / output control means 14. An end signal indicating the normal end of the transfer process is sent as an interrupt signal, and one cycle of data transfer ends.
[0007]
However, if the data transfer length specified by the read command from the higher-level device 20 is incorrect and the data transfer length is larger than the substantial data transfer length of the data stored in the data buffer 13, the SCSI Since it becomes impossible for the interface 11 to read data of the transfer length as set from the data buffer 13 and transfer it to the host device 20, the data transfer processing in the SCSI interface 11 does not end and the input / output control means 14 There is a problem that the end signal from the interface 11 is not returned and the input / output control means 14 cannot start the next process related to data transfer.
[0008]
The illegal length detecting means 15 is provided to avoid such a problem.
[0009]
The illegal length detection means 15 detects that illegal length data has been read from the data buffer 13 to the SCSI interface 11 and sends an illegal length detection signal to the input / output control means 14 as an interrupt signal, thereby enabling The data transfer process in the SCSI interface 11 is forcibly terminated by a command from the control means 14, and the SCSI interface 11 is reset by a command from the input / output control means 14. Allow processing to begin.
[0010]
FIG. 9 is a diagram illustrating a conventional process when an illegal length data transfer is performed in which the data transfer length specified by the read command from the host device 20 is larger than the substantial data transfer length of the data stored in the data buffer 13. This will be briefly described with reference to FIG.
[0011]
First, the input / output control means 14 sets the data transfer length specified by the read command from the host device 20 in the SCSI interface 11 (step b1), and outputs a data transfer command to the SCSI interface 11 (step b2). , The data transfer process by the SCSI interface 11 is started.
[0012]
In this case, since the data transfer length specified by the read command is an illegal data transfer larger than the substantial data transfer length of the data stored in the data buffer 13, the SCSI interface 11 sets the transfer length as set. Cannot be read from the data buffer 13 and transferred to the higher-level device 20.
[0013]
Therefore, the data transfer processing of the SCSI interface 11 does not end normally, no end signal is returned from the SCSI interface 11 to the input / output control means 14, and the input / output control means 14 Waiting for the interruption of the length detection signal, the time when the interruption of the illegal length detection signal is detected, that is, the illegal length data read into the SCSI interface 11 from the data buffer 13 by the data transfer processing of the SCSI interface 11, When it is confirmed that the data has been transferred to the storage device 20 (step b3), a forced termination command is sent to the SCSI interface 11 (step b4).
[0014]
When the SCSI interface 11 receives the forced termination command from the input / output control means 14, the SCSI interface 11 interrupts the data transfer process and outputs a forced termination completion signal indicating that the data transfer process has been forcibly terminated as an interrupt signal. It is sent to the control means 14. However, the values of the registers, counters, and the like used in the internal processing of the SCSI interface 11 are undefined due to the interruption of the data transfer processing. In this state, the SCSI interface 11 normally starts the next data transfer processing. May be unable to do so.
[0015]
Therefore, the input / output control unit 14 that has detected the forced termination completion signal from the SCSI interface 11 (step b5) further sends a reset command to the SCSI interface 11 (step b6).
[0016]
After the SCSI interface 11 that has detected the reset command initializes the values of the internal registers and counters, a reset end signal indicating that preparation for the next data transfer process is completed is used as an interrupt signal, and the input / output control means 14 To send to.
[0017]
Finally, when the input / output control means 14 detects the reset end signal from the SCSI interface 11 (step b7), one cycle of processing relating to the transfer of the data of the incorrect length is completed.
[0018]
However, the exchange of the forced termination command and the forced termination completion signal, the reset command and the reset termination signal, and the interruption control of the data transfer processing in the SCSI interface 11 are not related to the substantial data transfer processing. This is a control without data, that is, an overhead that may cause a reduction in the reliability and efficiency of the processing operation.
[0019]
As a data input / output device with reduced overhead, for example, as disclosed in Patent Document 1, data transfer required by comparing a data transfer length requested by a host device with a buffer length of a data buffer is disclosed. A “file device control device” has been proposed in which the number of times is obtained, data transfer is repeatedly executed by the number of times, and the result notification during this time is omitted to reduce overhead.
[0020]
[Patent Document 1]
JP-A-4-373054 (paragraph number 0015, FIG. 2)
[0021]
[Problems to be solved by the invention]
However, the “file device control device” disclosed in Patent Literature 1 simply makes the transfer process continuous in order to reduce the number of overheads caused by the result notification between the higher-level device and the storage device. , And more specifically, an overhead caused by an incorrect length data transfer request, more specifically, a forced termination command, a forced termination completion signal, a reset command, a reset termination signal exchanged between the SCSI interface and the input / output control means, In addition, this does not reduce the interruption control of the data transfer processing.
[0022]
[Object of the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a data input / output device capable of greatly reducing overhead caused by an illegal length data transfer request and improving the efficiency and stability of transfer processing.
[0023]
[Means for Solving the Problems]
The present invention relates to a higher-level device-side interface connected to a higher-level device, a lower-level device-side interface connected to a storage device, and data used for temporary storage of data passed between the higher-level device-side interface and the lower-level device-side interface. A buffer, and input / output control means for controlling the upper device-side interface and the lower device-side interface,
The input / output control means sets the data transfer length in the higher-level device-side interface and outputs a data transfer command to start the data transfer process by the higher-level device-side interface,
Upon receiving the data transfer command, the higher-level device-side interface executes data transfer processing for transferring data stored in the data buffer to the higher-level device based on the data transfer length set by the input / output control means. Sending an end signal to the output control means,
A data input / output device configured to start the next process related to data transfer by the input / output control unit that has received the end signal;
To achieve the above objectives,
Data length detecting means for detecting the data transfer length of the data stored in the data buffer;
The input / output control unit compares the data transfer length commanded by the host device with the data transfer length detected by the data length detection unit and compares the smaller data transfer length with the host device interface. A configuration is provided in which a data transfer length selection setting function to be set is provided.
[0024]
According to the above configuration, first, the data transfer length of the data stored in the data buffer is detected by the data length detecting means, and further, the input / output control means controls the data transfer length and the data length specified by the host device. After comparing the magnitude relation with the data transfer length detected by the detecting means, the smaller data transfer length is set in the higher-level device-side interface.
Therefore, if there is a data transfer request of an incorrect length from the host device, that is, if the data transfer length specified by the host device is larger than the substantial data transfer length of the data stored in the data buffer, The substantial data transfer length of the data stored in the data buffer is set in the higher-level device-side interface.
Next, the input / output control unit outputs a data transfer command to the higher-level device-side interface, whereby the data transfer process by the higher-level device-side interface is started.
At this time, the upper device-side interface executes the data transfer process based on the data transfer length set by the input / output control means, that is, the substantial data transfer length of the data stored in the data buffer. Therefore, the data transfer length set by the input / output control means matches the data transfer length of the data read from the data buffer, and the data transfer process is normally terminated as in the case of the positive-length data transfer. An end signal can be sent to the input / output control means.
Therefore, internal processing required for data transfer includes setting of a data transfer length from the input / output control means to the higher-level device-side interface, transmission of a data transfer command, and input / output control from the higher-level device-side interface. It is only necessary to send an end signal to the means.
As described above, the exchange of the forced termination command and the forced termination completion signal, the reset command and the reset termination signal which have been conventionally required in the transfer of the illegal length data, and the data transfer processing in the higher-level device-side interface are further performed. Since the interruption control is not required, the overhead associated with the transfer of the illegally-length data is reduced, and the efficiency and stability of the transfer process are achieved.
[0025]
Further, the data length detecting means can be configured to detect the data transfer length based on the format information of the data stored in the data buffer.
[0026]
Detecting the data transfer length by directly using the format information of the data eliminates the need for special arithmetic processing for detecting the transfer length, thereby realizing high-speed internal processing.
[0027]
Further, the data length detecting means may be configured to detect the data transfer length of the data based on the difference between the start address and the end address of the data stored in the data buffer.
[0028]
In this case, a simple subtraction process is required to detect the data transfer length, but there is an advantage that the transfer length of data having no format information can be reliably detected.
[0029]
Further, a determination function for determining the presence / absence of format information of the data stored in the data buffer is provided in the data length detecting means, and when there is format information, the data transfer length is detected based on the format information. If there is no information, the data transfer length of the data can be detected based on the difference between the start address and the end address of the data stored in the data buffer.
[0030]
In this case, high-speed internal processing can be realized for data having format information by omitting the arithmetic processing for detecting the transfer length. The data transfer length can be reliably detected by the subtraction processing.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the actual paper form of the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing a configuration of a data input / output device 1 according to an embodiment of the present invention.
[0032]
The data input / output device 1 includes a SCSI interface 11 (upper device interface) connected to a higher device 20 via a SCSI bus, a drive interface 12 (lower device interface) connected to a storage device 30, and a SCSI interface. A data buffer 13 for temporarily storing data when data is exchanged between the drive interface 11 and the drive interface 12 is provided in the same manner as in the related art.
[0033]
The data length detection means 2 is for detecting the data transfer length of the data stored in the data buffer 13, and is a component unique to this embodiment.
The data length detection means 2 is provided with a determination function for determining the presence or absence of format information of the data read in advance from the storage device 30 and stored in the data buffer 13. The data transfer length of the data is specified based on the format information of the data stored in the buffer 13. If the data has no format information, the start address and the last address of the data stored in the data buffer 13 are determined. The data transfer length of the data is obtained by taking the difference from the address.
[0034]
The input / output control means 3 has functions similar to those of the related art required for controlling the SCSI interface 11 and the drive interface 12, and further has a data transfer length and data length detection means 2 commanded by the host device 20. A data transfer length selection setting function is provided for comparing the magnitude relation with the detected data transfer length and setting the smaller data transfer length in the SCSI interface 11.
[0035]
Next, a process performed by the input / output control unit 3 when a read command from the host device 20 is input to the data input / output device 1 will be described with reference to the flowchart of FIG.
[0036]
When a read command from the host device 20 is input to the data input / output device 1, the input / output control unit 3 first reads the data transfer length specified by the read command from the host device 20 via the SCSI interface 11. (Step a1), and the actual data transfer length of the data stored in the data buffer 13 is detected via the data length detecting means 2 (step a2).
As described above, if format information is attached to the data stored in the data buffer 13, the data length detecting means 2 specifies the data transfer length of the data based on the format information, If there is no information, a difference between the start address and the end address of the data stored in the data buffer 13 is obtained, and this value is set as a substantial data transfer length of the data.
[0037]
Next, the input / output control unit 3 executes a process of comparing the magnitude relationship between the data transfer length specified by the read command from the host device 20 and the data transfer length detected by the data length detection unit 2 (step a3). ).
[0038]
If the data transfer length detected by the data length detection means 2 is larger than the data transfer length specified by the read command from the higher-level device 20 (the determination result in step a4 is Yes), the read command from the higher-level device 20 While the data transfer length specified by the above, that is, the smaller data transfer length is set in the SCSI interface 11 (step a6), the data transfer length specified by the read command from the host device 20 is determined by the data length detection means. If the data transfer length detected by the data length detection unit 2 is larger than the data transfer length detected by the data length detection unit 2 (No in step a4), the data transfer length detected by the data length detection unit 2, that is, the smaller data transfer length is transmitted to the SCSI interface 11. It is set (step a5).
[0039]
Next, the input / output control unit 3 outputs a data transfer command to the SCSI interface 11 to start the data transfer process by the SCSI interface 11 (step a7), and then outputs an end signal indicating a normal end of the data transfer process. Is input from the SCSI interface 11 as an interrupt signal.
[0040]
On the other hand, the SCSI interface 11, which has started the data transfer process in response to the data transfer command from the input / output control means 3, reads the data from the data buffer 13 based on the data transfer length preset by the input / output control means 3, and This data is transferred to the host device 20.
[0041]
Here, if the data transfer length specified by the read command from the higher-level device 20 is incorrectly longer than the substantial data transfer length of the data stored in the data buffer 13, the SCSI transfer is performed. Since the data transfer length detected by the data length detection means 2, that is, the substantial data transfer length of the data stored in the data buffer 13, has already been set in the interface 11 (see step a5), The data transfer length set by the output control means 3 and the data transfer length of the data read from the data buffer 13 match, and the SCSI interface 11 performs the data transfer processing in exactly the same way as the positive-length data transfer processing. Upon completion of the normal operation, an end signal can be sent to the input / output control means 3.
[0042]
Therefore, the input / output control means 3 sends a forced termination command to the SCSI interface 11 in order to forcibly terminate the data transfer of the illegal length, causes the SCSI interface 11 to execute the forced termination process, or indicates the completion of the forced termination process. It is not necessary to return the forced termination completion signal from the SCSI interface 11 to the input / output control means 3. Also, a reset command for initialization is sent from the input / output control means 3 to the SCSI interface 11, and a reset end signal indicating completion of the initialization processing is fed back from the SCSI interface 11 to the input / output control means 3. There is no need to do anything. In this manner, signal exchange and internal processing that are not directly related to the data transfer processing are not required, and the overhead associated with data transfer of an illegal length is greatly reduced.
[0043]
Then, the end signal sent from the SCSI interface 11 is detected by the input / output control means 3 in exactly the same way as in the case of the data transfer processing of the positive length (step a8), and the end of the data transfer processing of one cycle is recognized. The input / output control means 3 can immediately start the next processing, for example, the next data transfer processing.
[0044]
On the other hand, when the data transfer length detected by the data length detection means 2 is an illegal length data transfer or a positive length data transfer larger than the data transfer length specified by the read command from the higher-level device 20 Since the data transfer length specified by the read command from the host device 20 is set in the SCSI interface 11 as in the related art (see step a6), the SCSI interface 11 transmits the data of the transfer length as set. It is possible to read the data from the data buffer 13 and transfer it to the host device 20. The SCSI interface 11 normally terminates the data transfer process and sends an end signal to the input / output control means 3 in the same manner as in the past, and Can be completed.
[0045]
【The invention's effect】
The data input / output device of the present invention detects the substantial data transfer length of the data stored in the data buffer and compares the magnitude relationship between the data transfer length commanded by the host device and the substantial data transfer length. Then, the data transfer length of the smaller value is set in the higher-level device-side interface and the data transfer process is started, so that the data transfer length specified by the higher-level device is substantially equal to the data stored in the data buffer. Even if an illegal data transfer longer than the typical data transfer length is performed, the data transfer length set by the input / output control means to the higher-level device-side interface and the data transfer length of the data read from the data buffer. Can be matched normally, without forcibly interrupting the data transfer process at the higher-level device-side interface. It is possible to completion.
As a result, the exchange of the forced termination command and the forced termination completion signal, and the reset command and the reset termination signal, which were required for controlling the higher-level device-side interface that executes the data transfer of the illegal length, and in the higher-level device-side interface This eliminates the need for interruption control of data transfer processing, reduces overhead associated with data transfer of an illegal length, and achieves efficient and stable data transfer processing.
[0046]
In addition, when the configuration for detecting the data transfer length based on the format information of the data stored in the data buffer is applied, no special arithmetic processing for detecting the transfer length is required, and the algorithm for detecting the transfer length is not required. , But high-speed internal processing is realized.
[0047]
On the other hand, when the configuration for detecting the data transfer length based on the difference between the start address and the end address of the data stored in the data buffer is applied, even if the data does not have format information, the transfer length is determined. Can be reliably detected. Moreover, since the detection of the transfer length is realized by a simple subtraction process, there is no concern that the algorithm of the transfer length detection complicates or slows down the internal processing.
[0048]
Furthermore, the presence or absence of format information of the data stored in the data buffer is determined. If there is format information, the data transfer length is detected based on the format information. The data transfer length is detected based on the difference between the start address and the end address of the data. Internal processing can be realized, and the transfer length of data can be quickly and reliably detected by simple subtraction processing even for data having no format information.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of a data input / output device according to an embodiment to which the present invention is applied.
FIG. 2 is a flowchart showing a data transfer process by the data input / output device of the embodiment.
FIG. 3 is a functional block diagram showing a configuration of a conventional data input / output device.
FIG. 4 is a flowchart showing a data transfer process performed by a conventional data input / output device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Data input / output device 2 Data length detection means 3 Input / output control means 10 Data input / output device 11 SCSI interface (host device side interface)
12 Drive interface (lower device side interface)
13 data buffer 14 input / output control means 15 illegal length detection means 20 host device 30 storage device

Claims (4)

A higher-level device-side interface connected to a higher-level device, a lower-level device-side interface connected to a storage device, and a data buffer used for temporary storage of data passed between the higher-level device-side interface and the lower-level device-side interface; Input / output control means for controlling the upper device side interface and the lower device side interface,
The input / output control means sets a data transfer length in the higher-level device-side interface and outputs a data transfer command to start data transfer processing by the higher-level device-side interface,
The higher-level device-side interface receiving the data transfer command performs a data transfer process of transferring data stored in the data buffer to the higher-level device based on the data transfer length set by the input / output control unit. Execute and send an end signal to the input / output control means,
In the data input / output device configured to start the next process related to data transfer, the input / output control unit that receives the end signal includes:
Along with data length detection means for detecting the data transfer length of the data stored in the data buffer,
The input / output control unit compares the data transfer length instructed by the host device with the data transfer length detected by the data length detection unit, and compares the smaller data transfer length with the data transfer length. A data input / output device, which is provided with a data transfer length selection setting function to be set in a device-side interface. 2. The data input / output according to claim 1, wherein said data length detecting means is configured to detect a data transfer length of the data based on format information of the data stored in the data buffer. apparatus. The data length detecting means is configured to detect a data transfer length of the data based on a difference between a start address and an end address of the data stored in the data buffer. 2. The data input / output device according to 1. The data length detection means has a determination function of determining the presence or absence of format information of the data stored in the data buffer, and if there is format information, detects the data transfer length of the data based on the format information On the other hand, when there is no format information, the data transfer length of the data is detected based on the difference between the start address and the end address of the data stored in the data buffer. The data input / output device according to claim 1, wherein

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