-safe version: Unsigned int read_seqbegin_irqsave (seqlock_t *lock, unsigned long flags); int Read_seqretry_irqrestore (seqlock_t *lock,unsigned int seq, unsigned long flags);The writer must obtain a mutex when entering a critical section protected by Seqlock: void Write_seqlock (seqlock_t *lock); void Write_sequnlock (seqlock_t *lock);Since write locks are implemented using spin locks, spin locks control write access, so common variants of the spin lock can be used: void Write_seqlock_irqsave (
This procedure uses the dynamic mapping method to control the LED, the hardware platform is the ok6410 of the Flying LingLed.h: Defining control commands#ifndef _led_h#define _led_h#define led_magic ' M ' #define LED_ON _io (led_magic, 0) #define Led_off _io (LED _magic, 1) #endif Driver LED.C#include Application Led_app.c#include Compile the program, use the command Mknod/dev/leddev C 252 0 To create the device node, the main device number through the Cat/proc/devicesRunning the application
In the Linux authoring process, there are two files that we must understand and know. One of these is the Kconfig file, and the other is the makefile file. If you are familiar with it, then it is certainly necessary for the kernel to compile the. config file, in the. config file, we found that some modules were compiled into the kernel, and some just generated a module. In the middle, how do we let the kernel discover the modules we write, which we ne
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 () of bio processing.Since the data in our block
transaction.The following is a method of using the struct with the C99 syntax, and the struct member that does not show the declaration is initialized to null by GCCstatic const struct File_operations Globalmem_fops = {. Owner = This_module,. Llseek = Globalmem_llseek,. Read = Globalmem_read,. write = Globalmem_write,. Unlocked_ioctl = globalmem_ioctl,/* in the kernel version of 2.6.x, in the file operation structure,Will have the IOCTL field, use Unlocked_ioctl in the higher version */. open =
/IP network configuration file associated with the NIC is:/etc/sysconfig/network-scripts/ifcfg-ethx. where x starts at 0, the first Ethernet configuration file is:/etc/sysconfig/network-scripts/ifcfg-eth0. Use the VI Editor to modify this file, or you can modify the network card MAC address.Put Hwaddr=ff:ff:ff:ff:ffChange to Macaddr=00:1f:d0:64:9b:b7 macaddr behind is your MAC address2./etc/sysconfig/networking/profiles/default/ifcfg-eth0Put Hwaddr=ff:ff:ff:ff:ffChange to Macaddr=00:1f:d0:64:9b:
file has a. h file, which is the path of. h Modules: $ (make)-C $ (kernel_dir) m=$ (PWD) modules #$ (make)-i$ (INCLUDE)-C $ (Kernel_dir) m=$ (PWD) modules//if the. C file has an. h file, use this compilation syntax. Phony:modules Cleanc Lean: $ (make)-C $ (kernel_dir) m=$ (PWD) cleanElseobj-M: = gpio-sama5d3-Test.oendifAfter you have finished writing the above two files, save the exit.# makeThe. ko file is generated# insmod ****.ko-------Mount Drive#lsmod--------to view mounted
Linux driver module parameters-Linux Device DriversModule Parameters
In many cases, we expect to control our drive behavior through parameters. For example, because of different systems, to ensure good portability of our drivers, sometimes we want to control our driven behavior by passing parameters. In this way, drivers
With the release of Linux2.6, the drivers for each device are rewritten to varying degrees due to the new changes made by the 2.6 kernel. For the convenience of Linux enthusiasts, I put my own share out of this worthless file. This article lists the vast majority of changes in the 2.6 kernel with previous versions, but unfortunately the use of individual functions is not listed in detail due to limited time
question: I want to know what modules are built into the kernel in the Linux system and what parameters each module has. Is there a way to get a list of built-in modules and device drivers, along with their detailed information?
The modern Linux kernel is growing rapidly over time to support a large number of hardware, file systems, and network functions. During
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_transfer (d EV, Req->sector, req->current_nr_sectors, req->buffer, Rq_data_dir (req)); en
In the fourth chapter of the book "Linux device Drivers", we specialize in the debugging technology in driver development.PRINTK is just one of the techniques that requires PRINTK to print messages and write to files on disk, which slows down the entire code execution speed.There are also debugging techniques, and the effect on Code execution speed is smaller than prink.In this, we can have the driver creat
);
Read-copy-update
Read-copy-update (RCU) is also an advanced mutex mechanism.
Rarely used in drivers
Http://www.rdrop.com/users/paulmck/rclock/intro/rclock_intro.html
Optimized for situations where reads are frequent and rarely written
The protected resource should be accessed through a pointer
When the data structure needs to be modified, the write thread replicates first,
Skb_release_data function has 0xc4 so large, and oops occurs at 0x74 place. So let's take a look at where the Skb_release_data starts:#grep Skb_release_data./system.mapC0282AF4 T Skb_release_dataSo we know that when the system error occurs, the program pointer is c0282af4+0x74=c0282b68(2) Then use GDB to view the GDB./vmlinux (executed under the Linux directory) and enter debug mode.gdb$ b *0xc0282b68Breakpoint 1 at 0xc0282b68:file NET/CORE/SKBUFF.C,
1. Linux Power Management Global architectureLinux power management is very complex, involving system-level standby, frequency-voltage transformation, System idle processing, and each device driver support for system standby and runtime power management for each device, which can be say and every device driver in the system.Power management is very important for consumer electronics products. Therefore, this part of the work often occupies a considera
the Linux structure for continued use.Overall analysis-ReconstructionIf your project does not have a tight schedule, and you can use the portability code repeatedly for future projects, you will analyze the current RTOS application structure based on the time, and how to map them to the Linux structure. For RTOS application code, you need to consider ing RTOS tasks one by one to the viability of
1. Write Linux device driver, require engineers have a certain hardware foundation, know how SRAM, Flash, SDRAM, disk read and write,The interface of UART, I²c, USB and other devices, polling, interrupt, DMA principle, PCI bus working mode and CPU memory management MMU.2. Have a good C language Foundation, can flexibly use the structure, pointers, function pointers and memory dynamic application and release.3. Have a certain
knowledge involved in the chapter, but this is my idea during the review.I learned about arm-Linux. Except for the first chapter, other code is run on ARM9, the kernel version I used is the 2.6.29 kernel I used during learning.
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· Linux Device Driver Summary (1): basic concepts related
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