【文件属性】:
文件名称:mmap and DMA
文件大小:635KB
文件格式:PDF
更新时间:2013-09-08 11:55:02
mmap and DMA
mmap and DMA:This chapter delves into the area of Linux memory management, with an emphasis
on techniques that are useful to the device driver writer. The material in this chapter
is somewhat advanced, and not everybody will need a grasp of it. Nonetheless,
many tasks can only be done through digging more deeply into the memory management
subsystem; it also provides an interesting look into how an important part
of the kernel works.
The material in this chapter is divided into three sections. The first covers the
implementation of the mmap system call, which allows the mapping of device
memory directly into a user process’s address space. We then cover the kernel
kiobuf mechanism, which provides direct access to user memory from kernel
space. The kiobuf system may be used to implement ‘‘raw I/O’’ for certain kinds
of devices. The final section covers direct memory access (DMA) I/O operations,
which essentially provide peripherals with direct access to system memory.
Of course, all of these techniques requir e an understanding of how Linux memory
management works, so we start with an overview of that subsystem.