Char driver mmap

 · The mmap() operation is a request from userspace to map some source into its virtual address space. The way that the userspace program identifies which source it is interested in is by supplying a file descriptor (which is really just a handle on a resource known to the kernel).. This means that you have to make your device representable as a file descriptor so Reviews: 5. Device Access (Character Drivers) Access to a device by one or more application programs is controlled through the open(9E) and close(9E) entry points. The open(9E) routine of a character driver is always called whenever an open(2) system call is issued on a special file representing the device. For a particular minor device, open(9E) can be called many times, but the .  · If your driver need to support mmap a memory offset, then obvious there is a issue. In this case, you can just pass virt_to_phys (read_buff)PAGE_SHIFT in place. It is not recommended to use kmalloc to allocate the memory for remap purpose, as it is required to be page aligned, you can just use the kernel page APIs, like get_free_page to.

Device driver memory mapping¶ Memory mapping is one of the most interesting features of a Unix system. From a driver's point of view, the memory-mapping facility allows direct memory access to a user space device. To assign a mmap() operation to a driver, the mmap field of the device driver's struct file_operations must be implemented. The character device driver framework of Linux provides the ability to map device memory into a user space process address space A character driver may implement the mmap() function which a user space application can call The mmap() function creates a new mapping in the virtual address space of the calling process. mmap() and munmap() functions are provided by sys/mman.h library. so in order to use we need to include them like below. #include Syntax. As mmap() provides flexible memory mapping it has a lot of parameters to use. void *mmap(void *addr, size_t lengthint " prot ", int " flags, int fd, off_t offset).

vma->vm_file = file; return 0; } static struct file_operations simple_fops = { mmap: simple_mmap, open: simple_open, release: simple_release, };. Linux Device Driver Training. We will discuss character, block and network drivers, Implementing mmap() in a driver. mmap driver implementation,软件开发平台及语言笔记大全(超详细) __func__, a) struct dentry* file1; struct mmap_info { char* data; /* the data */ int.