linux device drivers 4th edition

No_llseek Access control for device files Exclusive equipment The most blunt method of access control is to allow only one process to open the device at a time Restrict access by only one user at a time Requires two data items An open count UID of the device owner

Preface Linux is a variant of the UNIX operating system, and the principle and idea of writing a driver in Linux is similar to that of other Unix systems, but it is very different for drivers in DOS or window environments. Design the driver in the Linux environment, the thought is concise, the operation is convenient,

atomic items that must be transmitted, and the direction of the transmission void Set_dma_mode (unsigned int channel, char mode); Mode Dma_mode_read Dma_mode_write Dma_mode_cascade Release control of the bus void set_dma_addr (unsigned int channel, unsigned int addr); void Set_dma_count (unsigned int channel, unsigne

function defined. The kernel assigns an empty page to it.*/struct page * (*nopage) (struct vm_area_struct *vma, unsigned long address, int *type);/* Before the User space access page. The function agrees that the kernel will pre-load these pages into memory.*/Int (*populate) (struct vm_area_struct *vm, unsigned long address, unsigned long len, pgprot_t prot, unsigned long pgoff, I NT Nonblock);Memory-mapped processingEach process in the system (in addition to some of the auxiliary threads in th

　　 Step 2: Create the int init_test (void) function) Register the device here: Result = register_chrdev (254, "test", test_fops ); 　　 (2) set test. copy c to the/uclinux/linux/drivers/char directory, and mem in the/uclinux/linux/drivers/char directo

the device here: Result = register_chrdev (254, "test", test_fops ); 　　 　　 (2) set test. copy c to the/uclinux/linux/drivers/char directory, and mem in the/uclinux/linux/drivers/char directory. in c, add the following code to the int chr_dev_init () function: # Ifdef CONFI

blocking and non-blocking IO in Linux device drivers:Blocking and non-blocking in 1.Linux device drivers Summary: http://m.blog.csdn.net/blog/dongteen/17264501Blocking and non-blocking io:http://m.blog.csdn.net/blog/dongteen/17264501 in 2.

the methods in the previous chapter to see information about this device in SYSFS:# Ls/sys/block/simp_blkdevDev holders range removable size slaves stat subsystem uevent#We found that our driver was missing the queue subdirectory in the SYSFS directory.It's not surprising, or it's going to freak out.In this chapter we implement our own make_request function to deal with bio, which is to get rid of the I/O Scheduler and the General __make_request () o

Sys_select ()------> Do_select ()The final call to the file descriptor fd corresponds to the struct file type variable of the struct file_operations *f_op of the poll function.The function that poll points to returns information that is currently read and written.1) returns read and write information if it is currently readable or writable.2) If it is not currently read/write, block the process and wait for the driver to wake up, call the poll function again, or return the timeout.3, the driver

*/Unregister_chrdev_region (MKDEV (mem_major, 0), 2); /* Release the device number */}Module_author ("David Xie");Module_license ("GPL");Module_init (Memdev_init);Module_exit (Memdev_exit);(3) app-ioctl.c(application)#include #include #include #include #include "memdev.h"/* contains the command definition */int main (){int fd = 0;int cmd;int arg = 0;Char buf[4096]; /* Open the device file */FD = ope

In the Linux kernel, The framebuffer (POST buffer) driver is the display driver standard. framebuffer abstracts the display device as the POST buffer. After the user maps the memory to the process address space, you can directly perform read/write operations, and write operations can be immediately displayed on the screen. Related display drivers and interfaces a

1.1 Linux device driver classification Linux device drivers occupy a large proportion of the Linux kernel source code, and the length of the source code is increasing, mainly the increase of the driver. During the continuous upgr

Relationship between Linux Device Drivers and the entire hardware System 1. device classification and features the hardware of a computer system consists of CPU, memory, and peripherals. With the development of the IC (Integratedcircuit) manufacturing process, the current chip integration is getting higher and higher,

and the typical user-space malloc.(Simple heap-based memory allocation technology)The kernel uses special page-based allocation techniques to optimally utilize system RAM.Linux handles memory allocations by creating a series of memory object pools in which the size of the memory blocks in each pool is consistent. SecretariatWhen a request is assigned, a whole block is passed directly to the requestor in a pool that contains a sufficiently large chunk of memory.The kernel can allocate only a few

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}};static struct Dm9000_plat_data Mini2440_dm9k_pdata = {The number of digits in the data line is 16 bits, and no e2prom is used. Flags = (Dm9000_platf_16bitonly | Dm9000_platf_no_eeprom),. dev_addr = {0x08,0x90,0x90,0x90,0x90,0x90},//mac address};static struct Platform_device Mini2440_device_eth = {. Name = "dm9000",//device name. id =-1,. num_resources = Array_size (Mini2440_dm9k_resource),. Resource = Mini2440_dm9k_resource,//Resources. Dev = {. Pl

in the queue, and returns null if none. Do not delete this request after processing struct Sbull_dev *dev = Req->rq_disk->private_data ; if (! blk_fs_request (req)) {//Determine if a file system request is not a block device request PRINTK (kern_notice "Skip non-fs request.\ n "); end_request (req, 0); continue; } The//sbull_transfer () function is a real processing block device request function Sbull

It may be difficult to put the driver model in the first chapter, but as long as the driver model can be crossed, it will be much easier later. The driver model is the cornerstone of the entire Linux Device Driver. Most people call the driver model a device model, but I have checked the help document of Linux to find t

Basic conceptsBlock Devices (Blockdevice)---is a random access device with a certain structure, the reading and writing of this device is block -based, he uses buffer zone to hold temporary data, waiting for the condition to mature, from the cache once written to the device or from the device to read the buffer at once

The learning of Linux device drivers is a huge project. Readers must first master the following basics.1. writing Linux device drivers requires engineers to have a good hardware foundation, understand the reading and writing metho