CN104866236A - Data reading method and equipment for storage media - Google Patents

Abstract

The invention relates to the field of data storage, in particular to a data reading method and equipment for storage media, and is used for solving the problem that storage media in handheld devices cannot be used as USB mounting media to be communicated with upper computers. The method comprises the following steps: a handheld device is connected with an upper computer through a USB, and sends information of a block storing preset content and information of a page to the upper computer after receiving a query command from the upper computer; the handheld device reads the stored preset content according to the information of the block after receiving a reading command from the upper computer, and sends the preset content to the upper computer through the USB; the handheld device sends a reading operation accomplishment command to the upper computer after determining the fact that the volume of data transmitted to the upper computer reaches the data volume required to be read. According to the invention, as a fat file system is not required to be loaded in the process that the upper computer performs reading operation on the storage media in the handheld device, the problem that storage media in handheld devices cannot be used as USB mounting media to be communicated with upper computers is solved.

Description

Data reading method and device for storage medium

The application of the present invention is a divisional application of the invention application with the filing date of July 10, 2012, the application number of 201210237930.X, and the invention title of "Data Reading Method and Device for Storage Medium".

technical field

The invention relates to the field of data storage, in particular to a method and device for reading data from a storage medium.

Background technique

As an open source code and free operating system, Linux system has been widely used in various embedded fields. Universal Serial Bus (Universal Serial Bus, USB) has become an extremely important method for embedded devices to communicate with other devices due to its high-speed transmission speed and versatility in the industry.

For example, after a handheld device (such as a mobile phone) using the Linux operating system is connected to a host computer (such as a PC) via USB, it can transmit data at high speed and can be used for charging, etc., so that the handheld device can play a role in storage devices, wireless network cards and Debugging and other functions.

At present, after the handheld device is connected to the PC through USB, the process of transferring data to the PC is roughly as follows:

Step 1: The PC sends a data reading command to the handheld device;

Step 2: After the handheld device receives the data reading instruction, it analyzes the data reading instruction to obtain the address information of the storage medium (such as a TF card) used to store the data, etc.;

Step 3: The handheld device calls the fat file system. Since the fat file system manages the information of each storage medium in the handheld device, the fat file system can find the corresponding storage medium according to the address information obtained by parsing, and read the storage medium by performing a read operation. The data in the medium, send the read data to the USB; the USB transfers the data to the PC;

Step 4: After the PC receives the data transmitted by the USB, it performs a display operation on the data, etc.

The storage medium that can transmit data to the PC through USB in the handheld device using the Linux operating system is called the USB mount medium under Linux. The requirement for the USB mount medium under Linux is that the medium can be accessed through the fat file system, which adds restrictions to the storage medium itself. For other storage mediums usually used in embedded devices, such as nand Flash, due to the limitations of its storage structure, etc., cannot load the fat file system, so the storage medium cannot be used as a USB mount medium to communicate with the PC.

Contents of the invention

Embodiments of the present invention provide a method and device for reading data from a storage medium, which are used to solve the problem that the storage medium in the handheld device cannot be used as a USB mount medium to communicate with a host computer because the fat file system cannot be loaded.

An embodiment of the present invention provides a method for reading data from a storage medium, including:

The handheld device is connected to the host computer through the Universal Serial Bus USB, and after receiving the query command from the host computer, sends the information of the block storing the prefabricated content and the information of the storage medium page to the host computer;

The handheld device receives the read command of the host computer, reads the stored prefabricated content according to the information of the block, and sends the prefabricated content to the host computer through USB;

The handheld device determines that the amount of data transmitted to the upper computer reaches the amount of data that needs to be read generated according to the information of the page, and sends a read operation completion command to the upper computer.

Since the handheld device in the embodiment of the present invention is connected to the host computer via USB, after receiving the query command from the host computer, it reports the information of the block and the page to the host computer, and after receiving the read command from the host computer Finally, according to the information of the block, the prefabricated content stored in the block can be read, and the read prefabricated content can be transmitted to the host computer through USB. Therefore, in the embodiment of the present invention, the reading operation of the host computer to the storage medium in the handheld device is realized, and the fat file system does not need to be loaded in the process, thereby solving the problem that the storage medium in the handheld device cannot load the fat file system. The problem that it cannot be used as a USB mount medium to communicate with the host computer.

Optionally, after sending the prefabricated content to the host computer via USB, it also includes:

The handheld device determines that the amount of data transmitted to the host computer does not reach the amount of data that needs to be read generated according to the information of the page, and continues to execute the step of reading the stored prefabricated content according to the information of the block.

Optionally, after the handheld device is connected to the host computer through the Universal Serial Bus USB, before receiving the query command from the host computer, it also includes:

The kernel layer of the handheld device reports the USB insertion event to the user layer, and after receiving the USB insertion event, the user layer reads the address of the mtd partition that stores the prefabricated content from the mtd partition list maintained, and reads the The address of the mtd partition is sent to the kernel layer;

The kernel layer of the handheld device receives the address of the mtd partition sent by the user layer, executes a read operation of the mtd partition corresponding to the address, and obtains the information of the block storing the prefabricated content in the mtd partition.

Optionally, the handheld device reads the stored prefabricated content according to the block information, specifically including:

The handheld device generates a logical block address LBA according to the information of the block, and converts the LBA into an address offset on the storage medium, and determines the block in the mtd partition pointed to by the address offset, Reads the prefab content stored in the identified block.

Optionally, before the handheld device is connected to the host computer via USB, it also includes:

The handheld device obtains the address of the mtd partition that stores prefabricated content in the storage medium of the handheld device, scans the partition corresponding to the address through the bad block management function of the mtd device, determines the bad block in the mtd partition, and saves the bad block Block information is recorded in a static array;

After the handheld device determines the block in the mtd partition pointed to by the address offset and before reading the prefabricated content stored in the determined block, it further includes:

The handheld device determines that the block pointed to by the address offset is not a bad block according to the recorded bad block information.

Optionally, if the handheld device determines that the block pointed to by the address offset is a bad block, after determining that the block pointed to by the address offset is a bad block, the handheld device further includes:

After the handheld device updates the current address offset to the address offset of the next good block of the current block, it reads the prefabricated content of a page size in the block pointed to by the updated address offset, and The read prefabricated content is transmitted to the host computer through USB.

An embodiment of the present invention provides a handheld device, including:

The information reporting unit is used to connect to the upper computer through the universal serial bus USB, and after receiving the query command of the upper computer, send the information of the block storing the prefabricated content and the information of the storage medium page to the upper computer machine;

The data reading reporting unit is used to receive the read command of the host computer, read the stored prefabricated content according to the information of the block, and send the prefabricated content to the host computer through USB; After the amount of data of the upper computer reaches the amount of data that needs to be read generated according to the information of the page, a read operation completion command is sent to the upper computer.

Optionally, the data reading and reporting unit is also used for:

After the prefabricated content is sent to the host computer via USB, it is determined that the amount of data transmitted to the host computer has not reached the amount of data that needs to be read generated according to the information of the page, and the execution is continued according to the information of the block. Steps to read stored prefab content.

Optionally, also include:

Kernel layer unit, after being connected with upper computer by universal serial bus USB, before receiving the inquiry command of described upper computer, after this handheld device is connected with upper computer by universal serial bus USB, send user layer unit Report the USB insertion event; receive the address of the mtd partition sent by the user layer unit, execute the read operation of the mtd partition corresponding to the address, and obtain the information of the block storing the prefabricated content in the mtd partition;

The user layer unit is configured to read the address of the mtd partition storing prefabricated content from the maintained mtd partition list after receiving the USB insertion event, and send the read address of the mtd partition to the kernel layer unit.

Optionally, the data reading and reporting unit is also used for:

The handheld device generates a logical block address LBA according to the information of the block, and converts the LBA into an address offset on the storage medium, and determines the block in the mtd partition pointed to by the address offset, Reads the prefab content stored in the identified block.

Description of drawings

Fig. 1 is a schematic flow chart of the method provided by the embodiment of the present invention;

FIG. 2 is a schematic diagram of a data reading process according to an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a device provided by an embodiment of the present invention.

Detailed ways

In order to solve the problem that the storage medium in the handheld device cannot be used as a USB mount medium to communicate with the host computer because the fat file system cannot be loaded, an embodiment of the present invention provides a method for reading data from the storage medium. The storage medium includes at least one memory technology device (mtd) partition, each mtd partition includes at least one block, and each block includes at least one page.

Referring to Fig. 1, the data reading method of the storage medium provided by the embodiment of the present invention comprises the following steps:

Step 10: After the handheld device is connected to the host computer via USB, obtain the address of the mtd partition that stores the prefabricated content in the storage medium of the handheld device, and obtain the block information that stores the prefabricated content in the mtd partition according to the address information, Specifically, it may include the number of blocks storing prefabricated content;

Step 11: The handheld device receives the query command from the host computer, and reports the block information to the host computer;

Step 12: The handheld device receives the read command from the host computer, which carries the logical block address (LBA) information generated by the host computer according to the information of the block, and determines the mtd partition that stores the prefabricated content pointed to by the LBA information The blocks in , read the prefabricated content stored in the determined block, and transmit the read prefabricated content to the host computer through USB.

Preferably, after the handheld device is connected to the host computer via USB and before obtaining the address of the mtd partition that stores the prefabricated content in the storage medium of the handheld device, the handheld device notifies the handheld device during the enumeration process of the handheld device by the host computer The device type of the handheld device on the upper computer is read-only. The read-only type may be an optical disc cdrom or the like.

Specifically, the address of the mtd partition storing the prefabricated content in the storage medium of the handheld device is obtained, and the information of the block storing the prefabricated content in the mtd partition is obtained according to the address information. The specific implementation method can be as follows:

The kernel layer of the handheld device reports the USB insertion event to the user layer. After receiving the USB insertion event, the user layer reads the address of the mtd partition that stores the prefabricated content from the maintained mtd partition list, and transfers the read mtd partition The address is sent to the kernel layer;

The kernel layer receives the address of the mtd partition sent by the user layer, executes a read operation on the mtd partition corresponding to the address, and obtains the information of the block storing the prefabricated content in the mtd partition.

Preferably, in step 11, while the handheld device reports the block information to the host computer, it also sends the page information of the storage medium to the host computer. Correspondingly, the read command received by the handheld device in step 12 can also be Carry the information of the amount of data that needs to be read generated by the host computer according to the page information;

Then, in step 12, after the handheld device transmits the read prefabricated content to the host computer via USB, it can judge whether the data volume that the host computer needs to read has been transmitted according to the information of the data amount, and if so, send a read to the host computer. The operation completes the command, otherwise, continue to read the prefabricated content, and transmit the read prefabricated content to the host computer through USB until the amount of data transmitted to the host computer reaches the amount of data that the host computer needs to read.

Preferably, before the handheld device is connected to the host computer via USB in step 10, the handheld device can obtain the address of the mtd partition that stores the prefabricated content in the storage medium of the handheld device, and scan the mtd partition corresponding to the address, Determine the bad blocks in the mtd partition according to the scan results, and record the information of the bad blocks;

Correspondingly, in step 12, after the handheld device determines the block in the mtd partition pointed to by the LBA information and before reading the prefabricated content stored in the determined block, it can judge the information pointed to by the LBA information according to the recorded bad block information. Whether the block is a bad block;

When judging that the block pointed to by the LBA information is not a bad block, read the prefabricated content stored in the determined block;

When judging that the block pointed to by the LBA information is a bad block, determine the block that is not marked as a bad block next to the block pointed to by the LBA information, read the prefabricated content stored in the block, and read the prefabricated The content is transmitted to the host computer via USB.

In this method, storage medium can be nand flash or embedded multimedia memory card (EmbeddedMultiMediaCard, EMC) etc.

Specific examples are as follows:

In this embodiment, it is necessary to pre-program the prefabricated content into the relevant mtd partition in the nand flash, and write the address information of the mtd partition into the mtd partition list. As shown in Figure 2, the follow-up process is as follows:

Step 20: After the handheld device is turned on, read the address of the mtd partition with prefabricated content stored in the nand flash of the handheld device from the maintained mtd partition list, scan the mtd partition corresponding to the address, obtain and record the mtd The bad block information in the partition, specifically, the bad block information can be recorded in a static array;

Here, the mtd partition is scanned to obtain and record the bad block information in the mtd partition. The specific implementation can be: scan each block of the current partition through the bad block management function of the mtd device, if the current block is a bad block , then add the address offset of this block to a bad block array to determine whether the block to be read is a bad block during subsequent read operations.

Step 21: After the handheld device is connected to the host computer via USB, the host computer establishes a data transmission path with the USB; the kernel layer of the handheld device notifies the host computer that the device type of the handheld device is a read-only type, such as a cdrom; The host computer executes the enumeration process of the handheld device;

Step 22: The handheld device loads the address of the mtd partition as the media mount point. Specifically, the kernel layer of the handheld device reports the USB insertion event to the user layer. After the user layer receives the USB insertion event, it starts from the maintained mtd partition list Read the address of the mtd partition that stores the prefabricated content, and send the read address of the mtd partition to the kernel layer;

Step 23: The kernel layer receives the address of the mtd partition sent by the user layer, executes the read operation of the mtd partition corresponding to the address, and obtains the number of blocks with prefabricated content stored in the mtd partition; the number of blocks with prefabricated content stored in the mtd partition The number will be pre-saved in the first block of the mtd partition;

The kernel layer initializes the reported content of the two commands of the read capacity command (Read capacity Command) and the read address command (Read TocCommand), so that the host computer can obtain the correct page size of the nand flash and the number of blocks storing prefabricated content. number. Read capacity Command is a small computer system interface (small computer system interface, scsi) command whose code is 0x25, and ReadToc Command is a scsi command whose code is 0x43.

After the initialization is completed, the kernel layer can send a notification of the completion of initialization to the upper computer;

Here, the reported content of the Read capacity Command mainly includes the number of blocks storing prefabricated content and the page size of the nand flash.

The reported content of the Read Toc Command mainly includes logical block addressing (logical block addressing, LBA) and minute-second frame (Minute, Second, Frame, MSF) information. The value of the initialized LBA is equal to the number of blocks that store prefabricated content in the mtd partition; the MSF information is the total playback duration information for playing the prefabricated content in the mtd partition as media, and the total playback duration information includes frame minutes, seconds, frame information.

Step 24: The host computer sends two commands, Read capacity Command and Read TocCommand, to the handheld device in sequence;

After the handheld device receives the Read capacity Command, it reports the number of blocks with prefabricated content stored in the initialized mtd partition and the page size information to the host computer;

After receiving the Read Toc Command, the handheld device reports the initialized LBA information and MSF information to the host computer.

Step 25: After the host computer obtains the relevant information, send a read command to the handheld device, such as the read_10 command, to read the nand flash; the read command carries the LBA generated by the host computer according to the number of blocks storing prefabricated content , and information about the amount of data that needs to be read;

The value of the LBA carried in the read command is an integer between 0 and the number of blocks storing prefabricated content in the mtd partition sent by the handheld device in step 24, for example, the number of blocks storing prefabricated content in the mtd partition is 5, if the host computer needs to read the content of the first block in the mtd partition, the value of the LBA carried in the read command is 1, and if it needs to read the content of the second block in the mtd partition, then the read command The value of the LBA carried in is 2, and so on. The amount of data to be read carried in the read command is the page size in nandflash or an integer multiple of the page size, because the data in nandflash is read in units of pages. The read_10 command is a scsi command whose code is 0x28;

The handheld device converts the LBA carried in the read command into the address offset on the nand flash, and obtains the size of the data that the host computer needs to read, and the converted address offset points to the mtd partition that the host computer needs to read The conversion method for storing blocks with prefabricated content is as follows: Since the block size of nand flash is generally 2048byte or 4096byte, and LBA is the number of blocks, the address offset after conversion is equal to LBA multiplied by the size of a block in the mtd partition.

Step 26: The handheld device judges whether the block pointed to by the current address offset is a good block according to the information of the bad block recorded in the step 20, if so, then go to step 27, otherwise, go to step 28;

Step 27: The handheld device reads the prefabricated content of a page size in the block pointed to by the current address offset, puts the read prefabricated content into the cache area, and proceeds to step 29;

Step 28: update the current address offset to the address offset of the next good block of the current block, and return to step 27;

Step 29: Send the prefabricated content in the cache area to the host computer via USB;

Step 30: The handheld device judges whether the current read operation is completed, that is, judges whether the amount of data to be read by the host computer has been transmitted, if so, go to step 31, otherwise, go to step 32:

Here, the handheld device judges whether the current read operation is completed, specifically: the amount of data to be read after the update, the amount of data to be read after the update is equal to the amount of data to be read before the update - the amount of data to be read this time ; If the amount of data to be read after updating is equal to 0, the current read operation is completed, otherwise it is not completed.

Step 31: The handheld device sends a read operation completion command to the host computer, notifying the host computer that the read operation is completed, and the process ends;

Step 32: Update the current address offset, the updated address offset is equal to the pre-update address offset minus the page size, and return to step 26.

The handheld device among the present embodiment can adopt the operating system of linux 2.6 version, and the page size of nand flash is 2kB, and total capacity is 512MB.

In this embodiment, through the method of directly accessing the nand flash, combined with the configuration of the scsi command, the upper computer can successfully obtain the required data, thereby completely reading out all the prefabricated contents of the mtd partition, and presenting it to the user in the form of a cdrom. Due to the read-only nature of the cdrom, it will not directly write to the nand flash, and there is no need to add a load balancing algorithm to the prefabricated content. Through the operation of prefabricated content to nandflash, the cost of the handheld device is reduced, a friendly usage method is provided to users, and the usage method of USB is expanded.

Referring to FIG. 3 , an embodiment of the present invention also provides a handheld device, including a storage medium, the storage medium contains at least one memory process device mtd partition, each mtd partition contains at least one block, and each block contains at least one page; the handheld Equipment also includes:

The information acquisition unit 31 is used to obtain the address of the mtd partition in the storage medium of the handheld device that stores the prefabricated content after the handheld device is connected to the host computer through the universal serial bus USB, and obtain the mtd partition according to the address information The block information of the prefabricated content is stored in ;

The information reporting unit 32 is used to receive the query command of the host computer, and report the information of the block to the host computer;

The data reading reporting unit 33 is used to receive the read command of the upper computer, which carries the logical block address LBA information generated by the upper computer according to the information of the block, and determines the mtd partition pointed to by the LBA information The blocks in , read the prefabricated content stored in the determined block, and transmit the read prefabricated content to the host computer through USB.

Further, the handheld device also includes:

The type reporting unit 34 is used to enumerate the handheld device in the host computer after the handheld device is connected to the host computer via USB and before obtaining the address of the mtd partition that stores prefabricated content in the storage medium of the handheld device. Notify the host computer that the device type of the handheld device is read-only.

Further, the information acquisition unit 31 includes:

The kernel layer unit reports the USB insertion event to the user layer unit after the handheld device is connected to the host computer through the universal serial bus USB; receives the address of the mtd partition sent by the user layer unit, and executes the mtd partition corresponding to the address Read operation to obtain the information of the block storing the prefabricated content in the mtd partition.

The user layer unit is configured to read the address of the mtd partition storing prefabricated content from the maintained mtd partition list after receiving the USB insertion event, and send the read address of the mtd partition to the kernel layer unit.

Further, when the information reporting unit 32 reports the information of the block to the host computer, it also sends the information of the page of the storage medium to the host computer; Information on the amount of data that needs to be read generated from the information on the above page;

The data reading and reporting unit 33 is also used for: after transmitting the read prefabricated content to the host computer via USB, judge whether the data volume that the host computer needs to read has been transmitted according to the information of the data amount, if so, then Send the read operation completion command to the upper computer, otherwise, continue to read the prefabricated content, and transmit the read prefabricated content to the upper computer through USB until the amount of data transmitted to the upper computer reaches the amount of data that needs to be read .

Further, the handheld device also includes:

The bad block marking unit 35 is used to obtain the address of the mtd partition that stores the prefabricated content in the storage medium of the handheld device before the handheld device is connected to the host computer through USB, and scan the mtd partition corresponding to the address. As a result, determine the bad blocks in the mtd partition and record the information of the bad blocks;

The data reading reporting unit 33 is further configured to: after determining the block in the mtd partition pointed to by the LBA information and before reading the prefabricated content stored in the determined block, according to the recorded bad block information, Judging whether the block pointed to by the LBA information is a bad block; when judging that the block pointed to by the LBA information is not a bad block, reading the prefabricated content stored in the determined block.

Further, the data reading and reporting unit 33 is also used for:

When judging that the block pointed to by the LBA information is a bad block, determine the block that is not marked as a bad block next to the block pointed to by the LBA information, read the prefabricated content stored in the block, and read the prefabricated The content is transmitted to the host computer via USB.

Further, the storage medium is nand flash.

In summary, the beneficial effects of the present invention include:

In the solution provided by the embodiment of the present invention, after the handheld device is connected to the host computer via USB, it obtains the address of the mtd partition that stores the prefabricated content in the storage medium of the handheld device, and obtains the prefabricated content stored in the mtd partition according to the address information. The block information of the content, after receiving the query command from the host computer, report the information of the block to the host computer, and after receiving the read command from the host computer, determine the information carried in the read command according to the block The generated LBA information points to a block storing prefabricated content, reads the prefabricated content stored in the block, and transmits the read prefabricated content to the host computer through USB. It can be seen that in this solution, the upper computer can read the storage medium in the handheld device, and the fat file system does not need to be loaded in this process, thus solving the problem that the storage medium in the handheld device cannot be used as a file system because the fat file system cannot be loaded. The problem of communication between the USB mount medium and the host computer.

The present invention utilizes the read-only feature of the cdrom to directly mount the mtd partition through the USB and the cdrom, and establishes a way for the host computer to directly access the nand flash through the USB, so that the large-capacity nandflash can prefabricate the content without loading the file system. The method of directly reading the prefabricated content in the mtd partition by connecting with the host computer through USB and cdrom reduces the cost of the handheld device, improves the utilization rate of nandflash and the diversity of USB mounting media.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (10)

1. A method for reading data from a storage medium, comprising: The handheld device is connected to the host computer through the Universal Serial Bus USB, and after receiving the query command from the host computer, sends the information of the block storing the prefabricated content and the information of the storage medium page to the host computer; The handheld device receives the read command of the host computer, reads the stored prefabricated content according to the information of the block, and sends the prefabricated content to the host computer through USB; The handheld device determines that the amount of data transmitted to the upper computer reaches the amount of data that needs to be read generated according to the information of the page, and sends a read operation completion command to the upper computer. 2. The method according to claim 1, characterized in that, after sending the prefabricated content to the host computer via USB, further comprising: The handheld device determines that the amount of data transmitted to the host computer does not reach the amount of data that needs to be read generated according to the information of the page, and continues to execute the step of reading the stored prefabricated content according to the information of the block. 3. The method according to claim 1 or 2, wherein, after the handheld device is connected with the host computer through the Universal Serial Bus USB, before receiving the query command of the host computer, it also includes: The kernel layer of the handheld device reports the USB insertion event to the user layer, and after receiving the USB insertion event, the user layer reads the address of the mtd partition that stores the prefabricated content from the mtd partition list maintained, and reads the The address of the mtd partition is sent to the kernel layer; The kernel layer of the handheld device receives the address of the mtd partition sent by the user layer, executes a read operation of the mtd partition corresponding to the address, and obtains the information of the block storing the prefabricated content in the mtd partition. 4. The method according to claim 1, wherein the handheld device reads the stored prefabricated content according to the information of the block, specifically comprising: The handheld device generates a logical block address LBA according to the information of the block, and converts the LBA into an address offset on the storage medium, and determines the block in the mtd partition pointed to by the address offset, Reads the prefab content stored in the identified block. 5. The method according to claim 4, wherein, before the handheld device is connected to the host computer via USB, further comprising: The handheld device obtains the address of the mtd partition that stores prefabricated content in the storage medium of the handheld device, scans the partition corresponding to the address through the bad block management function of the mtd device, determines the bad block in the mtd partition, and saves the bad block Block information is recorded in a static array; After the handheld device determines the block in the mtd partition pointed to by the address offset and before reading the prefabricated content stored in the determined block, it further includes: The handheld device determines that the block pointed to by the address offset is not a bad block according to the recorded bad block information. 6. The method according to claim 5, wherein if the handheld device determines that the block pointed to by the address offset is a bad block, then the handheld device determines that the block pointed to by the address offset After the block is a bad block, it also includes: After the handheld device updates the current address offset to the address offset of the next good block of the current block, it reads the prefabricated content of a page size in the block pointed to by the updated address offset, and The read prefabricated content is transmitted to the host computer through USB. 7. A handheld device, characterized in that, comprising: The information reporting unit is used to connect to the upper computer through the universal serial bus USB, and after receiving the query command of the upper computer, send the information of the block storing the prefabricated content and the information of the storage medium page to the upper computer machine; The data reading reporting unit is used to receive the read command of the host computer, read the stored prefabricated content according to the information of the block, and send the prefabricated content to the host computer through USB; After the amount of data of the upper computer reaches the amount of data that needs to be read generated according to the information of the page, a read operation completion command is sent to the upper computer. 8. The handheld device according to claim 7, wherein the data reading reporting unit is also used for: After the prefabricated content is sent to the host computer via USB, it is determined that the amount of data transmitted to the host computer has not reached the amount of data that needs to be read generated according to the information of the page, and the execution is continued according to the information of the block. Steps to read stored prefab content. 9. The handheld device according to claim 7 or 8, further comprising: Kernel layer unit, after being connected with upper computer by universal serial bus USB, before receiving the inquiry command of described upper computer, after this handheld device is connected with upper computer by universal serial bus USB, send user layer unit Report the USB insertion event; receive the address of the mtd partition sent by the user layer unit, execute the read operation of the mtd partition corresponding to the address, and obtain the information of the block storing the prefabricated content in the mtd partition; The user layer unit is configured to read the address of the mtd partition storing prefabricated content from the maintained mtd partition list after receiving the USB insertion event, and send the read address of the mtd partition to the kernel layer unit. 10. The handheld device according to claim 7, wherein the data reading reporting unit is also used for: The handheld device generates a logical block address LBA according to the information of the block, and converts the LBA into an address offset on the storage medium, and determines the block in the mtd partition pointed to by the address offset, Reads the prefab stored in the identified block.