Embedded Porting RTOS Device Drivers to （嵌入式RTOS的设备驱动程序移植到）.pdfVIP

http://0-.innopac.lib.ryerson.ca/10.1145/1020000/10179... Embedded Porting RTOS Device Drivers to Embedded Linux Transform your wild-and-woolly legacy RTOS code into well-formed Linux device drivers. by Bill Weinberg Linux has taken the embedded marketplace by storm. According to industry analysts, one-third to one-half of new embedded 32- and 64-bit designs employ Linux. Embedded Linux already dominates multiple application spaces, including SOHO networking and imaging/multifunction peripherals, and it now is making vast strides in storage (NAS/SAN), digital home entertainment (HDTV/PVR/DVR/STB) and handheld/wireless, especially in digital mobile phones. New embedded Linux applications do not spring, Minerva-like, from the heads of developers; a majority of projects must accommodate thousands, even millions of lines of legacy source code. Although hundreds of embedded projects have successfully ported existing code from such platforms as Wind Rivers VxWorks and pSOS, VRTX, Nucleus and other RTOSes to Linux, the exercise is still nontrivial. To date, the majority of literature on migration from legacy RTOS applications to embedded Linux has focused on RTOS APIs, tasking and scheduling models and how they map to Linux user-space equivalents. Equally important in the I/O-intensive sphere of embedded programming is porting RTOS application hardware interface code to the more formal Linux device driver model. This article surveys several common approaches to memory-mapped I/O frequently found in legacy embedded applications. These range from ad hoc use of interrupt service routines (ISRs) and user-thread hardware access to the semi-formal driver models found in some RTOS repertoires. It also presents heuristics and methodologies for transforming RTOS cod