Improvement And Optimization Of USB Mass Storage Driver On Linux Operating System

Accompany with the progress of embedding technology, embedded products such as intelligence mobile phone, PDA palm, digital camera, and mp4 emerged in a surprising speed. At the same time, the user requirement for the data transfer speed of storage device becomes higher and higher. Embedded product commonly adopts USB interface to communicate with PC. How to improve the transfer speed of mass storage device with USB interface is a pending problem in front of us.As Linux possesses merits such as small kernel, high efficiency, open source and etc, it becomes the preferred operating system of many embedded system. Started from analyzing Linux device mode, SD card driver, Linux kernel 2.6 realization for SCSI protocol, USB protocol, combining mass storage device driver on host and USB mass storage gadget driver on device, the paper figures out the concrete flow that data IO between device and host experience in Linux operating system, we find out that a IO request will be handled by file system, generi block layer, IO scheduler layer, SD card driver and etc, which lead the system expense is huge and slow transfer speed. Based on the analysis result mentioned above, the paper proposed an optimization scheme for USB mass storage device driver on Linux operating system. The main design is: when IO request reach the device, USB mass storage driver makes the IO dealing process skips file system, generi block layer and IO scheduler layer, directly mounting the IO request on the request queue of SD card driver, simplify the IO handle flow. Besides, based on the realization of this optimization, continually test and improvement, the paper enhanced read speed from the original 2MB/s to 10MB/s, improved the write speed from the original 1MB/s to 8MB/s on the full speed mode.