Information about Device Driver
A device driver, or software driver is a computer program allowing higher-level computer programs to interact with a computer hardware device.
A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware is connected. 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.
Linux device drivers are built into the OS kernel, and thus get built for the appropriate bit-width automatically. Provided that sufficient technical information about the hardware is available, the Linux kernel team will write the drivers free of charge.[1][2][3] This absolves both hardware vendors and end users from having to worry about drivers.
Additionally, the device drivers can either be built as parts of the kernel or can be built separately as loadable modules. The Windows(TM) .sys files and Linux .ko modules are 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.
Thus drivers are usually written by software engineers who come from the companies that develop the hardware. 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 device drivers, mainly for use with free operating 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 well 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 Mac OS X called the I/O Kit.
A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware is connected. 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.
Purpose
A device driver simplifies programming by acting as a translator between a device and the applications or operating systems that use it. The higher-level code can be written independently of whatever specific hardware device it may control. Every version of a device, such as a printer, requires its own specialized commands. In contrast, most applications access devices (such as sending a file to a printer) by using high-level, generic commands, such as PRINTLN. The driver accepts these generic statements and converts them into the low-level commands required by the device.Design
Device drivers can be abstracted into logical and physical layers. Logical layers process data for a class of devices such as ethernet ports or disk drives. Physical layers communicate with specific device instances. For example, a serial port needs to handle standard communication protocols such as XON/XOFF that are common for all serial port hardware. This would be managed by a serial port logical layer. However, the logical layer needs to communicate with a particular serial port chip. 16550 UART hardware differs from PL-011. The physical layer addresses these chip specific variations. Conventionally, OS requests go to the logical layer first. In turn, the logical layer calls upon the physical layer to implement OS requests in terms understandable by the hardware. Inversely, when a hardware device needs to respond to the OS, it uses the physical layer to speak through the logical layer.Linux device drivers are built into the OS kernel, and thus get built for the appropriate bit-width automatically. Provided that sufficient technical information about the hardware is available, the Linux kernel team will write the drivers free of charge.[1][2][3] This absolves both hardware vendors and end users from having to worry about drivers.
Additionally, the device drivers can either be built as parts of the kernel or can be built separately as loadable modules. The Windows(TM) .sys files and Linux .ko modules are 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.
Development
Writing a device driver requires an in-depth understanding of how the hardware and the software of a given platform function. Drivers "...operate in a highly privileged environment and can cause disaster if they get things wrong..." [1] 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.Thus drivers are usually written by software engineers who come from the companies that develop the hardware. 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 device drivers, mainly for use with free operating 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 well 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 Mac OS X called the I/O Kit.
Device driver applications
Because of the diversity of modern hardware and operating systems, many ways exist in which drivers can be used. Drivers are used for interfacing with:- Printers
- Video adapters
- Network cards
- Sound cards
- Local buses of various sorts - in particular, for bus mastering on modern systems
- Low-bandwidth I/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
- Implementing support for image scanners and digital cameras
- For hardware:
- Interfacing directly
- 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
- 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)
Virtual device drivers
A particular variant of device drivers are virtual device drivers. They are used in virtualization environments, for example when an MS-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 emulate 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.Open drivers
Driver APIs
- Advanced Linux Sound Architecture (ALSA) - The standard modern Linux sound driver interface
- I/O Kit - an open-source framework from Apple for developing Mac OS X device drivers
- Installable File System (IFS) - a filesystem API for IBM OS/2 and Microsoft Windows NT
- Network Driver Interface Specification (NDIS) - a standard network card driver API
- Open Data-Link Interface (ODI) - a network card API similar to NDIS
- Scanner Access Now Easy (SANE) - a public domain interface to raster image scanner hardware
- Uniform Driver Interface (UDI) - a cross platform driver interface project
- Windows Display Driver Model (WDDM) - the new graphic display driver architecture for Windows Vista
- Windows Driver Foundation (WDF)
- Windows Driver Model (WDM)
See also
References
1. ^ Greg Kroah-Hartman. Linux kernel monkey log - Free Linux Driver Development!. Retrieved on 2007-05-23.
2. ^ Don Marti. Linux driver development project bears fruit. Retrieved on 2007-05-23.
3. ^ . Retrieved on 2007-06-14.
2. ^ Don Marti. Linux driver development project bears fruit. Retrieved on 2007-05-23.
3. ^ . Retrieved on 2007-06-14.
External links
- A discussion of drivers' future
- Microsoft Windows Hardware Developer Central
- Writing Device Drivers: A Tutorial
A computer program is one or more instructions that are intended for execution by a computer. Specifically, it is a symbol or combination of symbols forming an algorithm that may or may not terminate, and that algorithm is written in a programming language.
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Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. The hardware of a computer is infrequently changed, in comparison with software and data, which are "soft" in the
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bus (bidirectional universal switch) is a subsystem that transfers data or power between computer components inside a computer or between computers, and a bus typically is controlled by device driver software.
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In computer science, a subroutine (function, method, procedure, or subprogram) is a portion of code within a larger program, which performs a specific task and can be relatively independent of the remaining code.
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An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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In computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change in execution.
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An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper transparencies.
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XON/XOFF is software data flow communications protocol for controlling the flow of data between computers and other devices. X stands for transmitter. This is frequently referred to as "software flow control".
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The 16550 UART (universal asynchronous receiver transmitter) is an integrated circuit designed for implementing the electrical interface for serial communications. It is frequently used to implement the serial port for IBM PC compatible personal computers, where it is often
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kernel is the central component of most computer operating systems (OS). Its responsibilities include managing the system's resources (the communication between hardware and software components).
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In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. Typical platforms include a computer's architecture, operating system, or programming languages and their runtime libraries.
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An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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kernel space and user space. Kernel space is strictly reserved for running the kernel, device drivers and kernel extensions. In most operating systems, kernel memory is never swapped out to disk.
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Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software.[1] The term software engineering
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Manufacturing (from Latin manu factura, "making by hand") is the use of tools and labor to make things for use or sale. The term may refer to a vast range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw
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Free software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions only to ensure that further recipients can also do these things.
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Reverse engineering (RE) is the process of discovering the technological principles of a device or object or system through analysis of its structure, function and operation. It often involves taking something (e.g.
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Windows Driver Foundation (WDF) is a set of Microsoft tools that aid in the creation of high-quality, reliable drivers for Windows 2000 and later versions of Windows.
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The User-Mode Driver Framework is a device-driver development platform first introduced with Microsoft's Windows Vista operating system, and is also available for Windows XP. It facilitates the creation of drivers for certain classes of devices.
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In computer science, message passing is a form of communication used in concurrent computing, parallel computing, object-oriented programming, and interprocess communication. Communication is made by the sending of messages to recipients.
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The Kernel-Mode Driver Framework (KMDF) is a driver framework developed by Microsoft as a tool to aid driver developers create and maintain Kernel mode device drivers for Windows 2000[1] and later releases.
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Mac OS X (IPA: /mæk.oʊ.ɛs.tɛn/) is a line of graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers.
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The I/O Kit is an open-source framework in the XNU kernel that helps developers code device drivers for Apple's Mac OS X operating system. The I/O Kit framework was originally introduced as part of Apple's Rhapsody operating system that later became Mac OS X, and shared no
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Hardware is a general term that refers to the physical artifacts of a technology.It may also mean the physical components of a computer system.
Hardware historically meant the metal parts and fittings that were used to make wooden products stronger, more functional, longer
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Hardware historically meant the metal parts and fittings that were used to make wooden products stronger, more functional, longer
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An interface defines the communication boundary between two entities, such as a piece of software, a hardware device, or a user. It generally refers to an abstraction that an entity provides of itself to the outside.
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A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper transparencies.
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graphics processing unit or GPU (also occasionally called visual processing unit or VPU) is a dedicated graphics rendering device for a personal computer, workstation, or game console.
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Network Card
A 1990s Ethernet network interface controller card which connects to the motherboard via the now-obsolete ISA bus.
Connects to:
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A 1990s Ethernet network interface controller card which connects to the motherboard via the now-obsolete ISA bus.
Connects to:
- Motherboard via one of
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Sound Card
A Sound Blaster Live! Value card, a typical present-day PCI sound card
Connects to:
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A Sound Blaster Live! Value card, a typical present-day PCI sound card
Connects to:
- Motherboard via one of
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