One: Platform bus1.1 OverviewA realistic Linux device driver usually needs to be hooked up on a bus, which is not a problem for devices that are attached to PCI,USB,IIC,SPI, but in embedded systems,The Independent peripheral controller integrated in the SOC system, the peripherals attached to the SOC memory space are not attached to such a bus. Based on this background, Linux invented a kind of virtual bus, called Platform Bus, the correspondingThe
From one point of view, the role of a device driver is to provide a mechanism, not a policy. When writing drivers, programmers should pay particular attention to the following basic concept: When writing kernel code to access hardware, do not impose any specific policy on the user. Because different users have different needs, the driver should handle the problem of how to make the hardware available, and how to use the hardware problem left to the up
Path for Linux Device Driver engineers-device model (top) Underlying model
K-style
Reprinted please indicate from Hengyang Normal University 08 electric 2 Y-kee http://blog.csdn.net/ayangke,QQ:843308498
I. Important knowledge points
1. sysfs File System
The sysfs file system is a special file system similar to the proc file system. It exists in the memory and is mounted to the memory by the kernel when th
1. Overview
2. system initialization platform device
3. The driver uses platform device
1. Overview
The Linux-2.6.11 introduces the concept of a device model that mounts most device drivers to a virtual bus.
Its purpose is:
1) provides friendly user interfaces. You can find the corresponding drivers and devices und
Every time I use a USB cable to plug in the computer interface will prompt "device can improve performance" small series always want to know the reason.
Today, when I go to the forum, I understand, share to everyone
is because your motherboard USB port is different has 1.1 of 2.0 of 3.0 because you plug in the USB port is relatively low so there will be a hint you can ignore him can also be inserted into the other mouth to try to plug in a better mo
Reason:Is that the virtual machine service is not turned onWorkaround: (Run as Administrator)Click "Start → run", enter CMD in the Run box to open a command prompt, then execute the following command in turn.net start VMCInet start vmx86net start Vmnetuserifsc config Vmci=autosc config Vmx86=autosc config Vmnetuserif=autoVMware cannot open the kernel device "\\.\global\vmx86": the system cannot find the file specified. Have you rebooted after installi
Now, let's write our own first character device driver--light LEDs. (Imperfect, back to perfect)
Hardware platform: Exynos4412 (FS4412)
Writing the drive is divided into the following steps:
A--View the schematic, data manual, understand the equipment operation method;
B-Find a similar driver in the kernel, develop it as a template, and sometimes need to start from scratch;
C-Implement driver initialization: For example, register the driver with the
Failure phenomenon:
When the WIN10 system uses a PIN to log on, it sometimes prompts "your device is offline, please log in with the last password used on this device."
Solution:
This time need to connect the network, re-enter the password to log in, you can connect to the wired network or wireless network, the following describes the connection network solution.
1. Click on the wireless i
When debugging, it is found that there is no selected device or the selected device Xcode does not support:
Workaround:
1. Download the DMG you need on the Internet to find out if you have any https://pan.baidu.com/s/1pLoxkDH?errno=0errmsg=Auth%20Login%20Sucess.
bduss=ssnerror=0traceid= #list/path=%2f
2.Finder Click "Apps" to find Xcode, right click to select "Show Package Contents" and go to "Con
Turn off eclipse.
Turn Adb.exe off in Task Manager
Enter the ADB directory and then execute the ADB start-server to successfully execute the problem resolution
The problem should be solved, but if adb start-server start up!Finally, the reason for the port occupancy is found.Here's how to fix it:1.adb nodaemon serverTo view the reasons that cannot be performed, output:
Cannot bind ' tcp:5037 '
2. Fixed a problem with the port! Yes, Port 5037 is occupied!3.netstat -ano | findstr
The following is my excerpt and translation, want to know more text at the end of the link ha ~Comparison of common values for-webkit-min-device-pixel-ratio ( is the physical pixel and device independent pixels on the device, device pixel ratio )Device resolution
Asynchronous device I/O Basics
Assume that a thread sends an asynchronous I/O Request to the device. This request is sent to the device driver, which is responsible for actual I/O operations. When the driver is waiting for the response from the device, the application thread is not suspended because it is waiting for t
I. Linux USB driver levels
1. devices, configurations, interfaces, and endpointsThe logical organization of a USB device consists of four layers: device, configuration, interface, and endpoint.
A device usually has one or more configurations:
Each USB device provides different levels of configuration information,
/*** Device_create-creates a device and registers it with sysfs* @ Class: pointer to the struct class that this device shoshould be registered* @ Parent: pointer to the parent struct device of this new device, if any* @ Devt: The dev_t for the char device to be added* @ Drvd
I. Overview
Speaking of writing I2C drivers in Linux, there are currently two main methods: one is to treat I2C devices as a common character device, the other is to use the Linux I2C driver architecture. The two drivers are compared below.
The advantages of the first method (corresponding to the disadvantages of the second method) include:● The idea is straightforward and you don't need to take the time to understand the complex I2C subsystem operati
How to use the platform device driver to write the driver:-------------------------------------------------------------------------1. Implement device orientation first:1) read the chip manual and obtain resources from the schematic diagram.2) construct a platform device structure and add platform Resources3) link our device
If you have multiple Android devices (including Android emulators) connected to your PC, you will need to use the Adb-s DeviceID shell when you enter the console. More trouble, this article has written a shell script file (need to be used under Linux or OS X, Windows needs to be newly written with bat or cmd).The basic idea is to use the ADB devices command to scan how many Android devices are connected to the PC, then intercept the device name from t
Recently encountered this problem of headache, baffled its solution, fools, cantilever thorn shares these things have done, finally see hope, so save, feel tidy share to everyone, hope to help.The initial understanding of cell phone resolution and web pixel is that it is twice times the difference.But what's puzzling is why we need 1.325 of this data, which is what it turns out to be:Give me a chestnut:The following is my excerpt and translation, want to know more text at the end of the link ha
As you know, on Windows IoT Core, if you use hardware such as a USB sound card and a camera with a microphone outdoors, you'll have multiple audio devices available. However, the system does not currently provide a direct UI to set the audio input or output device. After review, we can use the command line to change the default audio device, as follows.In the case of Raspberry Pi, I use a USB sound card, pl
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