JP4854483B2 - Data input / output device - Google Patents

Description

  The present invention relates to a data input / output device that has a controller having, for example, a DMA transfer function and performs data transfer with a connected device. In particular, the present invention relates to a data input / output device having a USB host controller and using mass storage communication using a file system for communication.

In general, in a controller driver that controls a controller having a DMA transfer function, a buffer effective for the DMA transfer function is provided to perform input / output by DMA transfer.
For example, in order to perform effective bulk transfer by DMA when using OHCI, which is one of the USB host controllers, it is desirable that the size of the buffer for DMA transfer is 8 KB unit with 4 KB unit as a boundary.

On the other hand, the upper layer that instructs the controller to input / output data is hierarchized into, for example, a file system and an application, and a necessary buffer is created in each layer, and data input / output is performed in the lower layer. I am instructing.
Furthermore, it is necessary to transfer data from a single application or file system to a connected device using a controller having a plurality of DMA transfer functions.

  Patent Document 1 relates to a data processing apparatus, and compares a prefetch address to a cache with a load instruction address. Here, an invention has been proposed in which, if they match, the storage from the main memory to the cache and the execution of the load instruction are performed simultaneously, and the data is directly loaded from the main memory without passing through the cache.

Patent Document 2 proposes an invention that uses a cache according to the type of data, in which information that is frequently written, such as FAT, is managed in the flash ROM and is buffered in a cache memory.
Patent Document 3 proposes an invention in which data is transferred from a flash ROM accessible in address units to a user memory without using a buffer.

Japanese Patent Laid-Open No. 5-143451 JP-A-9-97199 JP 2000-57039 A

  However, in a data input / output device including a controller having a conventional DMA transfer function, when data input / output is instructed from an upper layer having a data buffer, the following occurs. That is, in the controller driver that controls the controller having the DMA transfer function, the input / output data buffer instructed from the upper layer is created once for the DMA transfer and transferred to the buffer, and then the DMA transfer is performed. become.

  Further, in a file system that performs a cache operation of file data positioned in an upper layer of a controller driver, data input / output from an application is temporarily stored in a cache buffer and then transferred to the controller driver.

  For this purpose, each hierarchical system creates a unique data buffer, transfers data to the lower layer, and the lower layer temporarily transfers data input / output from the upper layer to the data buffer specific to each layer. In addition, data input / output and DMA transfer to a lower layer are performed. As a result, the memory utilization efficiency is reduced and unnecessary processing time is required.

When there are a plurality of controllers having a DMA transfer function, it is necessary to prepare a buffer effective for DMA transfer by a controller driver that controls each controller.
In Patent Document 1, data is directly loaded from the main memory without using a cache, and cannot be directly transferred from the DMA to the user memory.
Patent Document 2 is an invention in which data is cached according to data type, and is not involved in cache control using DMA transfer.
Patent Document 3 relates to data transfer between an accessible flash ROM and user memory in address units, and is different from cache control using DMA transfer.

  The present invention has been made in view of the above problems, and an upper layer that instructs data input / output to a controller driver that controls a controller having a DMA transfer function creates a data buffer effective for DMA transfer, and A data input / output device that enables direct input / output of data buffers input / output from the upper layer to the lower layer without creating a unique data buffer in each hierarchical system by instructing input / output The purpose is to provide.

A data input / output device of the present invention is a data input / output device that performs DMA transfer , and includes a controller driver that controls the data input / output device, the controller driver, and a first for data input / output to the controller driver. And a controller that uses a file system that performs file data caching operations, an application that uses the file system, and a second buffer for data input / output to / from the file system. Determining whether the first buffer starts on a boundary of a predetermined unit and satisfies a condition that is equal to or larger than a predetermined size, and if it is determined that the condition is satisfied, the first buffer is transferred to the DMA When it is determined that the condition is not satisfied, the DMA is set in the data buffer used for transfer. To create a data buffer to be used for feed.

According to the present invention, in a data input / output device that includes a controller having a DMA transfer function and performs data transfer with a connected device, an upper layer that instructs the controller driver that controls the controller to input / output data is DMA transfer. By creating a valid data buffer and instructing data input / output, the data buffer input / output from the upper layer is directly input / output to the lower layer without creating a unique data buffer in each hierarchical system. It becomes possible to do.
As a result, the processing time for data transfer and the memory utilization efficiency can be greatly improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a data input / output apparatus that has a controller having a DMA transfer function according to the present invention and performs data transfer with a connected device.

In FIG. 1, reference numeral 1 denotes a data input / output device having a USB host function, which has a DMA transfer function and a user buffer creation service suitable for DMA-specific transfer, such as a digital camera direct printer. .
The data input / output device 1 includes an application 4, a file system 5, and a USB host function 6.

  The application 4 creates a data buffer in a CPU (not shown), a RAM, a ROM, and a ROM (not shown) stored in the ROM (not shown). The file system 5 is stored in a ROM (not shown) and creates its data buffer in a RAM (not shown). The USB host function 6 includes a USB host controller having a DMA transfer function and a USB host controller driver that is stored in a ROM (not shown) that controls the controller and creates a data buffer in a RAM (not shown). The USB host controller driver requires a DMA data input / output buffer for controlling the data input / output device.

  The USB host function 6 is connected to the data input / output device 2 having a USB device function, which will be described later, by the USB communication unit 3 so as to be communicable such as a mass storage class.

In FIG. 1, reference numeral 2 denotes a data input / output device having a USB device function, for example, a digital camera that can be connected to a printer and execute direct printing.
The data input / output device 2 includes a USB device function 7 and a storage device 8.

  The USB device function 7 includes a CPU (not shown), a RAM, a ROM, a USB device controller, and a USB device controller driver stored in a ROM (not shown) that controls the controller. The storage device 8 performs input / output to / from a removable medium such as a compact flash (registered trademark) for realizing mass storage class connection in the USB communication means 3 described above.

  The application 4 uses a file system and requires a data input / output buffer to the file system. A data buffer for inputting / outputting data stored in the storage device 8 of the data input / output device 2 having the USB device function is created in a RAM (not shown) of the data input / output device 1 having the USB device function. Then, it instructs the file system 5 to input / output data.

  The file system 5 uses a USB host controller driver, requires a data input / output buffer to the controller driver, and performs a file data cache operation. In accordance with the data input / output instruction of the application 4, a cache buffer is created in the RAM (not shown) of the data input / output device 1 having the USB device function based on the sector information of the designated data, and the data input / output to the USB host function 6 Give instructions.

  The USB host controller driver constituting the USB host function 6 follows the data input / output instruction of the file system 5. Then, a USB data transfer buffer effective for the DMA function of the USB host controller is created in the RAM (not shown) of the data input / output device 1 having the USB device function, and data transfer by DMA is instructed.

  FIG. 2 is a flowchart of a data transfer program in the data input / output apparatus 1 that performs data transfer with a device 2 that has a controller having a DMA transfer function to implement the present invention.

  As described below, when it is determined that the data buffer input / output to / from the controller driver is a buffer suitable for transfer specific to DMA, the controller driver performs the following processing. That is, the controller driver does not create a data buffer input / output to / from a data input / output device having a DMA, and instructs the DMA transfer by performing a cache flush on the data buffer area input to the controller driver. Then, cache invalidation is performed on the data buffer area output from the controller driver to instruct DMA transfer.

  In step S100, a data buffer for inputting / outputting data stored in the storage device 8 of the data input / output device 2 having the USB device function from the application 4 is created in the data input / output device 1 having the USB device function. This is performed on the illustrated RAM. At that time, a user buffer creation service suitable for DMA transfer using DMA mounted on the USB host controller constituting the USB host function 6 is called. For example, when the USB host controller described above is OHCI, the user buffer to be created is created with a 4 KB boundary at the top.

  If there are a plurality of controllers having a DMA transfer function, a user buffer creation service is prepared for each controller suitable for the DMA of the controller. Then, the application 4 specifies a controller that communicates with a connection device that is a target of data input / output, and uses a user buffer creation service suitable for DMA included in the controller.

In step S110, the application 4 instructs the file system 5 to input / output data from the storage device 8 of the data input / output device 2 having the USB device function to the user buffer created in step S100.
In step S120, the data input / output data buffer instructed by the application 4 in the file system 5 is determined.

The file system 5 creates a cache buffer with a management block in units of sectors in order to cope with random access by the application 4.
When the data in the storage device 8 of the data input / output device 2 having the USB device function instructed to be input / output from the application 4 is a continuous sector and is larger than the management block size, the following occurs. The file system 5 does not create a data buffer for caching file data input / output to / from the controller driver. A data buffer input / output from / to the file system 5 from the application 4 is used as a data buffer input / output from / to the controller driver. That is, the user buffer created by the application is specified in step S100, and instructed to input / output data from the storage device 8 of the data input / output device 2 having the USB device function to the USB host function 6 in step S140 in units of management blocks. To do.

Based on the data buffer determination from the application 4 in step S120, cases are classified as follows.
When the data in the storage device 8 of the data input / output device 2 having the USB device function instructed to be input / output by the application 4 is not designated as a continuous sector larger than the management block size, the following is performed. . That is, in step S130, the file system 5 calls the user buffer creation service suitable for the DMA transfer using the DMA installed in the USB host controller constituting the USB host function 6 by the file system 5 to create the cache buffer for the management block. Do. In step S140, the created cache buffer is designated, and the USB host function 6 is instructed to input / output data from the storage device 8 of the data input / output device 2 having the USB device function.

When the data in the storage device 8 of the data input / output device 2 having the USB device function specified by the application 4 in step S110 is a set of a plurality of discontinuous sectors, the following is performed. In other words, the determination of the data buffer in step S120 may be performed in the management block in units of sectors constituting the cache buffer managed by the file system 5.
In step S150, the USB host controller driver constituting the USB host function 6 determines the data input / output data buffer instructed from the file system 5.

  It is determined whether the data buffer instructed to be input / output from the file system 5 is a buffer suitable for DMA transfer using the DMA of the USB host controller that constitutes the USB host function 6. For example, when the USB host controller is OHCI, the size of 8 KB from the boundary of 4 KB unit is an optimal data buffer for USB bulk transfer once.

  When the data input / output data buffer instructed by the file system 5 starts at the 4 KB unit boundary, the data buffer designated by the file system 5 is designated in step S140. In step S170, input / output of data from the storage device 8 of the data input / output device 2 having the USB device function is performed by DMA data transfer every 8 KB unit.

  In the data buffer determination from the file system 5 in step S150, if the data buffer instructed to be input / output from the file system 5 is not started at the boundary of 4 KB unit or the transfer designated size is less than 8 KB, It becomes as follows. That is, in step S160, a data buffer is created by calling a user buffer creation service suitable for DMA transfer using DMA mounted on the USB host controller constituting the USB host function 6 described above. Then, the created data buffer is designated, and in step S170, data is input / output from the storage device 8 of the data input / output device 2 having the USB device function by DMA data transfer.

  In the DMA transfer in step S170, if the data input is from the storage device 8 of the data input / output device 2, the above-described data buffer is cache invalidated, and then the DMA transfer is started. On the other hand, in the case of data output to the storage device 8 of the data input / output device 2, the above-described data buffer is cache flushed, and then DMA transfer is started.

  The above is the description of the embodiments of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions shown in the claims or the functions of the configurations of the embodiments are achieved. Any configuration that can be applied is applicable.

FIG. 3 is a block diagram illustrating a data input / output device that performs data transfer with a device having a controller having a DMA transfer function according to the present invention. It is a flowchart of the data transfer program in the data input / output device which performs a data transfer with the device which has a controller which has the DMA transfer function which implement | achieves this invention, and is connected.

Explanation of symbols

1 Data input / output device having USB host function 2 Data input / output device having USB device function 3 USB communication means 4 Application 5 File system 6 USB host function 7 USB device function 8 Storage device

Claims (3)

A data input / output device for performing DMA transfer,
A controller driver for controlling the data input / output device;
A file system for performing a cache operation of file data using the controller driver and a first buffer for data input / output to the controller driver;
An application using the file system and a second buffer for data input / output to / from the file system;
The controller driver is
Determining whether the first buffer satisfies a condition that starts at a predetermined unit boundary and is equal to or larger than a predetermined size;
When it is determined that the condition is satisfied, the first buffer is set as a data buffer used for the DMA transfer,
A data input / output apparatus that creates a data buffer used for the DMA transfer when it is determined that the condition is not satisfied . The controller driver is
If it is determined that the first buffer satisfies the condition ,
Instruct the DMA transfer by performing a cache flush to the data buffer ,
2. The data input / output device according to claim 1 , wherein a cache transfer is instructed to the data buffer to instruct DMA transfer. In the file system, the is continuous data instructed to input and output from the application, and if the management block is larger than the size of the first buffer for caching in the file system, wherein in the said file system controller Without creating the first buffer for caching file data input / output to / from the driver, a second buffer for storing data input / output to / from the file system from the application is input / output to / from the controller driver. 2. The data input / output device according to claim 1 , wherein the data input / output device is used as a first buffer for storing data.

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