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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
Device object (device_object) --------------- main Member I. device object (device_object) Kd> dt _ device_objectNtdll! _ Device_object+ 0x000 type: int2b+ 0x002 size: uint2b+ 0x004 referencecount: int4b+ 0x008 driverobject: ptr32 _ driver_object; driver object of the device+ 0x00c nextdevice: ptr32 _ device_object; points to the next
The tty core code tty_io.c contains the following lines of code: /* * Ok, now we can initialize the rest of the tty devices and can count * on memory allocations, interrupts etc.. */static int __init tty_init(void){ cdev_init(tty_cdev, tty_fops); if (cdev_add(tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) || register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") Several system-level terminal devices are created here. They are not real physical devices. Each of them creates these
The biggest feature of Linux devices is that device operations are like file operations. In the application layer, a hardware device is just a device file. Applications can operate hardware devices like operating files, such as open (), close (), read (), and write. Below is a simple implementation of the character device
Azure IoT technology research series 3-device-to-cloud, cloud-to-device communications, azureiot In the previous blog, we registered the simulated device to Azure IoT Hub: We got the unique identifier of the device. Azure IoT technology research series 2-device registration
Device number:1, self-allocation of the initiativeMajor = Register_chrdev (0, "First_drv", first_sdv_fops);//RegisterWhen you register your device with the device number 0, the kernel will voluntarily assign a master device number to return.2. Manual designationFind the main device
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
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
Linux Device Driver Programming-Linux general technology-Linux programming and kernel information-complex device driver-the following is a detailed description. The complex device drivers mentioned here involve PCI, USB, network devices, Block devices, and so on (strictly speaking, these devices are not in the same concept, for example, they are tied with Block d
In the Rt-thread 2.0.0 formal version of the introduction of PIN devices as miscellaneous devices, its device driver files pin.c in Rt-thread-2.0.1\components\drivers\misc, mainly for the operation of Chip Gpio, such as light led, Keys and so on. At the same time for the corresponding chip platform, you need to write the underlying GPIO driver, such as GPIO.C.One, in PIN.C defines a static PIN device object
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
I. What is IOCTL?IOCTL is a function used by the device driver to manage the device's I/O channels. The management of the I/O channel is to control some features of the device, such as the Serial Transmission baud rate and the motor speed. The number of calls is as follows: Int IOCTL (int fd, IND cmd ,...); FD is the File Identifier returned by the open function when the user program opens the
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
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