The audio system in Android is using the ALSA system architecture. Asoc--alsa System on Chip, is built on the standard ALSA drive layer, in order to better supportA software system for audio codec in embedded processors and mobile devices, ASOC is divided into three parts: machine, platform and codec in audio device drivers.Codec part: Responsible for audio decoding, this part of the code is completely non-platform-independent (the device is provided by the original), it contains some audio cont
To understand the Linux PCI device driver, first understand that the so-called Linux PCI device driver actually includesLinux PCI device drivers and Device Drivers. I do not know whether the reader understands this sentence. I think this sentence is very important. For drivers like PCI and USB, we must understand this concept, in order to understand how to look a
How to compile a Linux Device Driver
2006-12-10 16:52:36
LinuxIs a variant of the UNIX operating system. The principle and idea of writing a driver in Linux is similar to that in other UNIX systems, however, the drivers in the DoS or window environment differ greatly. In a Linux environment, the driver is designed with simple ideas, convenient operations, and powerful functions. However, it only supports a small number of functions and can only rely o
Development of uClinux drivers
Basic knowledge:
Kernel space ------- user space (memory application data exchange, etc)
Device ---- Device Driver ----- device No.
Driver category: character device block device network device
Interrupt handling
Driver development for uClinux and Linux is the same, but the debugging method is different. Learning driver development for uClinux is the process of learning the driver development for Linux. Linux driver debu
I have been learning device-driven programming for some time and have written several drivers. So I have a new understanding and understanding of the device driver. I have been learning device-driven programming for some time and have written several drivers. So I have a new understanding and understanding of the device driver.★What is a driver?
When I first started learning the device driver, there were a
Linux device driversOne, the role of device-drivenThe most popular explanation for device drivers is " Drive hardware Device Actions ". Drive and the underlying hardware directly to deal with, according to the specific work of the hardware device, read and write device registers, the completion of the device polling (polling (Polling) is a CPU decision how to provide peripheral equipment services, also known as "programmed output in" (programmed I/O).
The function of counting the number of words is encapsulated in the Linux driver. The Linux system maps each driver into a single file. These files are called device files or drive files and are stored in the/dev directory. The steps for writing a Linux driver are as follows:1. Build Linux drive skeleton (load and unload Linux drivers);2, registration and cancellation of equipment documents;3, specify the information related to the drive;4, specify th
Brief introduction
The name of the TTY device is abbreviated from the previous telex, originally referred to as a physical or virtual terminal connected to a UNIX system
The core of the Linux TTY driver is immediately below the standard character device driver layer and provides a range of functions that are used as interfaces by terminal type devices
There are three types of TTY drivers: console, serial, and Pty
/proc/tty
Hardware vendors usually update the device's drivers regularly, to modify bugs in older drivers, improve driver compatibility, and so on, in general, newer drivers often mean better performance and more reliable stability, which is what many friends see when a vendor publishes a new driver The main reason for the system driver to be updated immediately within the
This example is for Android up-Reading Exploration (vol. 1): The Demo sample program included with the HAL and Driver Development book. are now pasted out for inspection.Terminal operations, commands that may be used:Insmond Word_count.kolsmod | grep Word_count to see if the driver was successfully installed Rmmod WORD_COUNTDMESG | grep word_cout | Tail-n 2 View log information with Linux driver output Cat/var/log/syslong | grep Word_count | Tail-n 2modinfo Word_count.ko View driver informationD
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, line312This is to tell us in which file, in
will have to also." ”3, see example Drive, Linux kernel driver, generally have a relatively simple example code, specifically, see the first step of the TXT document. With this simple example code, we further clarify how the drive works.4, good, ready to work to complete, here should formally start. Write it yourself? No, or secretly lazy, online to find ready-made, there is just your chip driver, really lucky, direct use, of course, often can not be used directly, to debug under the next line.
code under default and clean starts with the TAB key.Third, compile the Globalvar modulePut the previous globalvar.c file and the makefile file in the same folder, I was placed in the Globalvar folder I created, go to the Globalvar folder, open the terminal, and then log in root permissions, enter the make command compile module. Four, write the test program of the Globalvar module, name it test_globalvar.c, the source code is as follows: #include Compile the test file in the terminal input Di
this driver"10. When the driver installation succeeds, you can see that the output of the debug message "Hello from Pnpdriver", the output statement you can find in the DriverEntry function of your source code.11. To end the debugging, remember to click "Debug"-"End debugging".12. The next time you continue debugging without restarting the virtual machine, you can use the built-in pipeline directly. Hit a breakpoint below to try.13. Commissioning situation:Problem Collection1. There are no VISU
, depending on the break flags to determine whether the send is completed or accepted.static irqreturn_t dm9000_interrupt (int irq, void *dev_id){if (Int_status ISR_PRS)-accepts data interrupts.Dm9000_rx (Dev);if (Int_status isr_pts)Dm9000_tx_done (dev, db);}static void Dm9000_tx_done (struct net_device *dev, board_info_t * db){Netif_wake_queue (Dev); --wake-up waiting queue}2.5 Data AcceptanceFor data acceptance, the data is actually read from the media buffer and then submitted to the upper
int Dma_map_device (struct device *dev,struct scatterlist *sg, int nents,enum dma_data_directiondirection);
There can be a relatively simple way to pre-allocate buffers in a Linux system, which is to synchronize the "mem=" parameter to reserve memory. For example, for a system with a memory of 64MB, passing the MEM=62MB command-line argument to it allowsThe top 2MB memory is reserved for use as IO memory, this 2MB memory can be statically mapped, can also execute Ioremap ().As wi
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 Linux kernel base, at least understand the interface between the driver
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