1. Mtp Usb Device Driver For Mac Os X
2. Linux Device Driver Tutorial

The Role of the Device Driver. 10 Chapter 1: An Introduction to Device Drivers Version Numbering Before digging into programming, we should comment on the version numbering scheme used in Linux and which versions are covered by this book. First of all, note that everysoftware package used in a Linux system has its own. The Role of the Device Driver 1.2. Splitting the Kernel. Debugging Support in the Kernel 4.2. Debugging by Printing. Access Control on a Device File 6.7. CHAPTER 3 Chapter 3 Char Drivers The goal of this chapter is to write a complete char device driver. We develop a char. Devices are managed by driver 7. Modern Linux kernels allow multiple drivers to share major numbers, but most devices that you will see are still organized on the. 'In scull, each device is a linked list of pointers, each of which points to a scull_dev structure.' NOW READS: 'In scull, each device is a linked list of pointers, each of which points to a scull_qset structure.'

Best way to get into Kernel programming? Ask Question. Up vote 8 down vote favorite. LDD (used to, at least) have exercises where you wrote virtual drivers, e.g. RAM disks, and virtual network devices. Someone already mentions the book 'Linux Device Drivers' - this is an excellent resource, and I highly recommend it as well. Linux Device Drivers, 3rd Edition: By Jonathan Corbet, Greg Kroah-Hartman, Alessandro Rubini. This bestselling guide has helped countless programmers learn how to support computer peripherals under the Linux operating system, and how to develop new hardware under Linux. MAC Address Resolution 17.12. Custom ioctl Commands 17.13.

I am working on a small embedded system. When my linux boots up into user space, I know where are my devices in the physical memory. I want to map them into user space virtual addresses. Currently, I am doing it through a kernel module. I use vmalloc/kmalloc (depending on the size) and then I use ioremap_page_range on that returned virtual addresses to map my physical addresses. I dont think that is the correct way to go about. First of all I am allocating memory and then I am asking kernel to remap that virtual address space to some different physical address space. (Initially mapped physical->virtual in vmcall/kmalloc is kinda useless as I dont care about those physical pages. This is definitely not good.)

Instead of this is there a better way to map the known physical memory into user space process. (I know other than my user space process, no one gonna touch that memory.)

Thanks

3 Answers

What you are trying to do is accessing what is called IO memory. I can only encourage you to read the Linux Device Drivers (LDD) book and more specifically the chapter 9.

To 'allocate' such an area, you need to call

. Before your driver can access it, you have to assign it a virtual address, this is done with a call to

To ensure that your driver will then work on different architectures/platforms, be sure to use some accessor function to such areas ( ioread8/16/32 or iowrite8/16/32 and all of their variants).

In Kernel module, remap_pfn_range() can be used to convert the physical address to virtual address. The following link will be helpful.

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In Kernel module, remap_pfn_range() can be used to convert the physical address to virtual address. When you don't have a actual devices you can:1) create a virtual device and,2) use mmap to those virtual devices to access the very same kernel memory through remap_pfn_range virtual mapping of that process.3) Usually in dedicated environments you may addition want to pin those physical pages lest they are taken away from your process.4) You also share these physical addresses with different processes but will need to handle synchronization, independently through other IPC mechanisms as to each process they will look as different addresses.

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In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer.^[1] A driver provides a software interface to hardware devices, enabling operating systems and other computer programs to access hardware functions without needing to know precise details about the hardware being used.

A driver communicates with the device through the computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device. Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface.^[2]

Purpose[edit]

The main purpose of device drivers is to provide abstraction by acting as a translator between a hardware device and the applications or operating systems that use it.^[1] Programmers can write higher-level application code independently of whatever specific hardware the end-user is using.For example, a high-level application for interacting with a serial port may simply have two functions for 'send data' and 'receive data'. At a lower level, a device driver implementing these functions would communicate to the particular serial port controller installed on a user's computer. The commands needed to control a 16550 UART are much different from the commands needed to control an FTDI serial port converter, but each hardware-specific device driver abstracts these details into the same (or similar) software interface.

Development[edit]

Writing a device driver requires an in-depth understanding of how the hardware and the software works for a given platform function. Because drivers require low-level access to hardware functions in order to operate, drivers typically operate in a highly privileged environment and can cause system operational issues if something goes wrong. In contrast, most user-level software on modern operating systems can be stopped without greatly affecting the rest of the system. Even drivers executing in user mode can crash a system if the device is erroneously programmed. These factors make it more difficult and dangerous to diagnose problems.^[3]

The task of writing drivers thus usually falls to software engineers or computer engineers who work for hardware-development companies. This is because they have better information than most outsiders about the design of their hardware. Moreover, it was traditionally considered in the hardware manufacturer's interest to guarantee that their clients can use their hardware in an optimum way. Typically, the Logical Device Driver (LDD) is written by the operating system vendor, while the Physical Device Driver (PDD) is implemented by the device vendor. But in recent years, non-vendors have written numerous proprietary device drivers, mainly for use with free and open sourceoperating systems. In such cases, it is important that the hardware manufacturer provides information on how the device communicates. Although this information can instead be learned by reverse engineering, this is much more difficult with hardware than it is with software.

Microsoft has attempted to reduce system instability due to poorly written device drivers by creating a new framework for driver development, called Windows Driver Foundation (WDF). This includes User-Mode Driver Framework (UMDF) that encourages development of certain types of drivers—primarily those that implement a message-based protocol for communicating with their devices—as user-mode drivers. If such drivers malfunction, they do not cause system instability. The Kernel-Mode Driver Framework (KMDF) model continues to allow development of kernel-mode device drivers, but attempts to provide standard implementations of functions that are known to cause problems, including cancellation of I/O operations, power management, and plug and play device support.

Apple has an open-source framework for developing drivers on macOS, called I/O Kit.

In Linux environments, programmers can build device drivers as parts of the kernel, separately as loadable modules, or as user-mode drivers (for certain types of devices where kernel interfaces exist, such as for USB devices). Makedev includes a list of the devices in Linux: ttyS (terminal), lp (parallel port), hd (disk), loop, sound (these include mixer, sequencer, dsp, and audio)..^[4]

The Microsoft Windows.sys files and Linux .ko modules contain loadable device drivers. The advantage of loadable device drivers is that they can be loaded only when necessary and then unloaded, thus saving kernel memory.

Kernel mode vs. user mode[edit]

Device drivers, particularly on modernMicrosoft Windows platforms, can run in kernel-mode (Ring 0 on x86 CPUs) or in user-mode (Ring 3 on x86 CPUs).^[5] The primary benefit of running a driver in user mode is improved stability, since a poorly written user-mode device driver cannot crash the system by overwriting kernel memory.^[6] On the other hand, user/kernel-mode transitions usually impose a considerable performance overhead, thereby prohibiting user-mode drivers for low latency and high throughput requirements.

Kernel space can be accessed by user module only through the use of system calls. End user programs like the UNIX shell or other GUI-based applications are part of the user space. These applications interact with hardware through kernel supported functions.

Applications[edit]

Because of the diversity of modern hardware and operating systems, drivers operate in many different environments.^[7] Drivers may interface with:

• Local buses of various sorts—in particular, for bus mastering on modern systems
• Low-bandwidthI/O buses of various sorts (for pointing devices such as mice, keyboards, USB, etc.)
• Computer storage devices such as hard disk, CD-ROM, and floppy disk buses (ATA, SATA, SCSI)
• Implementing support for different file systems

Common levels of abstraction for device drivers include:

• For hardware:
  • Interfacing directly
  • Writing to or reading from a device control register
  • Using some higher-level interface (e.g. Video BIOS)
  • Using another lower-level device driver (e.g. file system drivers using disk drivers)
  • Simulating work with hardware, while doing something entirely different^[8]
• For software:
  • Allowing the operating system direct access to hardware resources
  • Implementing only primitives
  • Implementing an interface for non-driver software (e.g. TWAIN)
  • Implementing a language, sometimes quite high-level (e.g. PostScript)

So choosing and installing the correct device drivers for given hardware is often a key component of computer system configuration.^[9]

Virtual device drivers[edit]

Virtual device drivers represent a particular variant of device drivers. They are used to emulate a hardware device, particularly in virtualization environments, for example when a DOS program is run on a Microsoft Windows computer or when a guest operating system is run on, for example, a Xen host. Instead of enabling the guest operating system to dialog with hardware, virtual device drivers take the opposite role and emulates a piece of hardware, so that the guest operating system and its drivers running inside a virtual machine can have the illusion of accessing real hardware. Attempts by the guest operating system to access the hardware are routed to the virtual device driver in the host operating system as e.g., function calls. The virtual device driver can also send simulated processor-level events like interrupts into the virtual machine.

Virtual devices may also operate in a non-virtualized environment. For example, a virtual network adapter is used with a virtual private network, while a virtual disk device is used with iSCSI. A good example for virtual device drivers can be Daemon Tools.

There are several variants of virtual device drivers, such as VxDs, VLMs, and VDDs.

Open source drivers[edit]

• Printers: CUPS
• RAIDs: CCISS^[10] (Compaq Command Interface for SCSI-3 Support^[11])
• Scanners: SANE
• Video: Vidix, Direct Rendering Infrastructure

Solaris descriptions of commonly used device drivers:

• fas: Fast/wide SCSI controller
• hme: Fast (10/100 Mbit/s) Ethernet
• isp: Differential SCSI controllers and the SunSwift card
• glm: (Gigabaud Link Module^[12]) UltraSCSI controllers
• scsi: Small Computer Serial Interface (SCSI) devices
• sf: soc+ or social Fiber Channel Arbitrated Loop (FCAL)
• soc: SPARC Storage Array (SSA) controllers and the control device
• social: Serial optical controllers for FCAL (soc+)

APIs[edit]

• Windows Display Driver Model (WDDM) – the graphic display driver architecture for Windows Vista, Windows 7, Windows 8, and Windows 10.
• Unified Audio Model (UAM)^[13]
• Windows Driver Foundation (WDF)
• Windows Driver Model (WDM)
• Network Driver Interface Specification (NDIS) – a standard network card driver API
• Advanced Linux Sound Architecture (ALSA) – as of 2009 the standard Linux sound-driver interface
• Scanner Access Now Easy (SANE) – a public-domain interface to raster-image scanner-hardware
• I/O Kit – an open-source framework from Apple for developing macOS device drivers
• Installable File System (IFS) – a filesystem API for IBM OS/2 and Microsoft Windows NT
• Open. WhatIs.com. TechTarget. Retrieved 19 March 2018.
• ^EMC Education Services (2010). Information Storage and Management: Storing, Managing, and Protecting Digital Information. John Wiley & Sons.
• ^Burke, Timothy (1995). Writing device drivers: tutorial and reference. Digital Press.
• ^'MAKEDEV — Linux Command — Unix Command'. Linux.about.com. 2009-09-11. Retrieved 2009-09-17.Cite web requires website= (help)
• ^'User-mode vs. Kernel-mode Drivers'. Microsoft. 2003-03-01. Archived from the original on 2008-03-09. Retrieved 2008-03-04.Cite uses deprecated parameter dead-url= (help); Cite web requires website= (help)
• ^'Introduction to the User-Mode Driver Framework (UMDF)'. Microsoft. 2006-10-10. Retrieved 2008-03-04.Cite web requires website= (help)
• ^Deborah Morley (2009). Understanding Computers 2009: Today and Tomorrow. Cengage Learning.
• ^Computer Peripherals and Interfaces. Technical Publications Pune. January 2008. pp. 5–8. ISBN8184314744. Retrieved 2016-05-03.
• ^'What are Device Drivers and why do we need them?'. drivers.com. April 17, 2015. Retrieved March 19, 2018.
• ^'CCISS'. SourceForge. 2010. Retrieved 2010-08-11. Drivers for the HP (previously Compaq) Smart Array controllers which provide hardware RAID capability.
• ^Russell, Steve; et al. (2003-10-21). 'Abbreviations and acronyms'. Server Consolidation with the IBM eserver xSeries 440 and VMware ESX Serve. IBM International Technical Support Organization. p. 207. ISBN0-7384-2684-9. Retrieved 2011-08-14.^{[permanent dead link]}
• ^'US Patent 5969841 - Gigabaud link module with received power detect signal'. PatentStorm LLC. Archived from the original on 2011-06-12. Retrieved 2009-09-08. An improved Gigabaud Link Module (GLM) is provided for performing bi-directional data transfers between a host device and a serial transfer medium.Cite uses deprecated parameter dead-url= (help); Cite web requires website= (help)
• ^'Unified Audio Model (Windows CE 5.0)'. msdn.microsoft.com. Retrieved 2016-09-19.
• ^'dxd - dynax driver framework: Main Page'. dxd.dynax.at. Retrieved 2016-09-19.

Mtp Usb Device Driver For Mac Os X

External links[edit]

Linux Device Driver Tutorial