What is a Device Driver, How Does Device Driver Works Explained, Computer Drivers, Computer Technology.In computing, a device driver is a computer program th. Latest Drivers in Input Devices Intel Wireless Bluetooth Driver 22.20.0 Intel Wireless Bluetooth is recommended for end users, including home users and business customers with Intel Wireless.
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Types of Drivers
Windows device drivers generally come in 2 flavors: Virtual Device Drivers (VXD) and Windows Driver Model (WDM). VxD style drivers are older, and are less compatible, while WDM drivers are supposed to be fully code-compatible all the way back to Windows 98.
In the old days of DOS, the computer was free land where anything goes. To that end, developers wrote their own hardware drivers, conforming to no specific specification or interface, using real-mode assembly code. With the advent of Windows 3.0, the operating system began to take a more hands-on approach to application management, by creating and maintaining a variety of virtual machines, to execute different programs in different processor contexts. Drivers could no longer exist as non-conformist real-mode DOS drivers, but instead had to mitigate access between multiple programs, running more or less in parallel with each other. Windows 3.0 changed the 'real devices' into managed resources known as 'virtual devices', and replaced the real-mode drivers with new virtual device drivers (VDD).
The Windows NT product line existed as a separate entity from the 'regular' windows brand. These two operating systems were completely different in almost every imaginable way, except perhaps that the shells looked similar. Windows NT was a fully-managed operating system, and unauthorized resource accesses were blocked by the NT kernel. This meant that in Windows NT, device drivers needed to interface with the computer through specific methods, while standard windows drivers (Windows 3.0, 3.1, 3.11, 95, 98, Me) could access hardware directly, without any sort of management. The drivers for both systems at this point, were generally written in assembly language, as well.
Realizing that the market was split between Windows and Windows NT, Microsoft saw a need to introduce a single driver model, so that device drivers could be portable between Windows and Windows NT. In addition, Microsoft knew that drivers had to be writable in a higher-level language, like C, in order to be code-compatible for different hardware systems. To meet these needs, Microsoft created the Windows Driver Model (WDM). WDM drivers are compiled using the DDK, they are written in C, and they follow exacting specifications that ensure they can be executed on any windows system. This book will attempt to focus on WDM drivers, but will include notes on writing DOS TSR drivers, and VDDs as well.
Device Drivers operate in kernel mode so writing, testing, and debugging drivers can be a tricky task. Drivers should always be well tested before they are installed.
Since device drivers do not operate in user mode, the user mode libraries (kernel32.dll, user32.dll, wingdi.dll, msvcrt.dll) are not available to a device driver. Instead, a device driver must link directly to ntoskrnl.exe and hal.dll which provide Native API and executive services.
Writing a Driver
Device drivers are typically written in C, using the Driver Development Kit (DDK). There are functional and object-oriented ways to program drivers, depending on the language chosen to write in. It is generally not possible to program a driver in Visual Basic or other high-level languages.
Because drivers operate in kernel mode, there are no restrictions on the actions that a driver may take. A driver may read and write to protected areas of memory, it may access I/O ports directly, and can generally do all sorts of very powerful things. This power makes drivers exceptionally capable of crashing an otherwise stable system.
The Windows platform DDK comes with header files, library files, and a command-line compiler that can be used to write device drivers in C or C++. There is no graphical interface to the DDK compiler.
Device Driver Stack
Windows implements device drivers in a highly-modular fashion, and it is important that we discuss some vocabulary before we continue the discussion of driver programming any further. The drivers necessary for any particular device are arranged in a driver stack, and are connected together internally by a singly-linked list, that starts at the bottom of the stack (the root driver), and terminates at the highest level driver. Each driver must contain at least 2 modules, a root driver, and a function driver. This combination, with some optional additions, constitute the whole of what people generally call a complete 'device driver'. Function Drivers will be the most common type of driver to be written, and will be of a primary focus in this wikibook.
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Microsoft realized that certain classes of devices all behave similarly, and it would be a gigantic waste of time for every hardware manufacturer to have to write the entire driver code from scratch. To this end, Windows allows for a type of driver known as a class driver. Class drivers are themselves not complete function drivers, but class drivers can be dynamically linked to a regular function driver, and can simplify the development process quite a bit. It is possible to write your own class driver, but 3rd party programmers generally don't worry about it. In general, Microsoft will supply the class drivers, and driver developers will tap into those class drivers. This ensures that class drivers are fully Microsoft tested and certified, and that they are very versatile.
Another classification of driver is the filter driver. There are two general types of filter driver, an upper filter driver, and a lower filter driver. Upper filter drivers exist in the stack above the function driver, and--as their name implies--they filter the incoming I/O requests. Lower filter drivers are placed in the stack between the function driver and the root driver. Filter drivers are generally implemented as bug fixes, or as quick hack extensions for preexisting drivers.
Here is a general diagram of a driver stack:
Buses and Physical Devices
For simplification, let us use the term 'bus' to refer to any place on your computer where information can travel from one place to another. This is a very broad definition, and rightfully so: the term 'bus' needs to account for everything from USB, Serial ports, PCI cards, Video outputs, etc. Each bus is controlled by its own root driver. There is a USB root driver, a PCI root driver, and so on.
Let's now consider a mythical construct known as the root bus, a structure that all other buses connect into. A root bus object doesn't actually physically exist in your computer, but it is handy to think about it. Plus, the root bus has its own driver. The root bus driver object is responsible for keeping track of the devices connected on any bus in your entire computer, and ensuring that the data gets to where it is all going.
Plug-n-Play (PnP) is a technology that allows for the hardware on the computer to be changed dynamically, and the PnP software will automatically detect changes, and allocate important system resources. PnP gets its own root driver, that communicates closely with the Root bus driver, to keep track of the devices in your system.
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Device Namespace, and Named Devices
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Drivers execute in the context of whatever thread was running when windows accessed the driver. To this end, we say that drivers execute in an 'arbitrary context'. Therefore, it is not good practice for a driver programmer to make any assumptions about the state of the processor at the entry point to a driver. There are a few issues that arise with this, so we will discuss them here.
Floating Point Arithmetic
Drivers that want to use MMX or floating point arithmetic may find they are in for some undue difficulty. Because a driver may be entered in any context, at any time, the floating point unit may contain partial results and unhandled exceptions from the user mode program that was interrupted to call the driver. It is not enough to simply save the context and then to restore it, because any unhandled exceptions may become 'unhandleable', and raise a system error or a bug check. There are only certain times when Microsoft recommends using floating point arithmetic, and we will discuss them later.
- Understanding the Windows Driver Model - An introduction to the basic concepts needed for WDM programming
- WDM I/O Concepts - Understanding the I/O concepts needed for WDM programming
- Kernel-Mode Driver Framework 1.11 - the .ISO download includes the Driver Development Kit (DDK)
Find information on known issues and the status of the rollout for Windows 10, version 20H2 and Windows Server, version 20H2. Looking for a specific issue? Press CTRL + F (or Command + F if you are using a Mac) and enter your search term(s).
Windows 10, version 20H2 is available for users with devices running Windows 10, versions 1903 and higher who manually seek to “Check for updates” via Windows Update. The recommended servicing status is Semi-Annual Channel.
Note We are slowly throttling up availability over the coming weeks to ensure a reliable download experience. As a result, the update may not be offered to you right away. For more details, see How to get the Windows 10 October 2020 Update.
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|Summary||Originating update||Status||Last updated|
|Some games might fail to open, or you might receive an error|
You might have issues with some Direct3D games when using in-game overlay feature of Discord.
|OS Build 19042.1000|
|Resolved External||2021-02-08 |
|Errors or issues during or after updating devices with Conexant ISST audio drivers|
Devices with affected Conexant ISST audio drivers might receive an error or have issues with Windows 10, version 2004.
|N/A ||Confirmed||2021-01-22 |
|Errors or issues during or after updating devices with certain Conexant audio drivers|
Devices with affected Conexant or Synaptics audio drivers might receive a stop error with a blue screen.
|N/A ||Confirmed||2021-01-05 |
|Automatic input of Furigana might not work as expected|
In certain circumstances, the automatic Furigana input/conversion feature may not work as expected in apps.
|N/A ||Mitigated||2020-12-10 |
Some games might fail to open, or you might receive an error
|Resolved External||OS Build 19042.1000|
|Last updated: 2021-02-08, 07:16 PT|
Opened: 2021-02-08, 06:29 PT
Microsoft and Discord have found incompatibility issues with some games using Direct3D 12 when the in-game overlay feature of Discord is enabled. When attempting to open affected games you might receive an error, or the game might close silently.
Workaround: To mitigate this issue, you can turn off the in-game overlay in settings within the Discord app.
Resolution: This issue is now resolved in an update to the Discord app. To verify you're on the latest version, right click on the Discord icon in the notification area and select 'Check for updates...'. If there are updates to install, it should install automatically but you might need to select the arrow icon in the upper right corner of the app to install the updated version. There is no update for Windows needed to resolve this issue.
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Automatic input of Furigana might not work as expected
|Mitigated||N/A ||Last updated: 2020-12-10, 06:24 PT|
Opened: 2020-12-03, 12:29 PT
When using the Microsoft Japanese Input Method Editor (IME) to enter Kanji characters in an app that automatically allow the input of Furigana characters, you might not get the correct Furigana characters and might need to enter them manually. Note for developers: Affected apps are using the ImmGetCompositionString function.
Workaround: To mitigate this issue, please follow the instructions in Revert to a previous version of an IME (Input Method Editor).
Next steps: We are working on a resolution and will provide an update in an upcoming release.
Errors or issues during or after updating devices with Conexant ISST audio drivers
|Confirmed||N/A ||Last updated: 2021-01-22, 01:43 PT|
Opened: 2020-05-27, 12:22 PT
Synaptics and Microsoft have found incompatibility issues with certain versions of drivers for Conexant ISST audio driver and Windows 10, version 2004 (the Windows 10 May 2020 Update). Windows 10 devices with affected Conexant ISST audio driver might receive an error or experience issues while installing the update or after the device has updated. The affected driver will be named Conexant ISST Audio or Conexant HDAudio Driver under Sound, video and game controllers in Device Manager and have file name uci64a96.dll through uci64a231.dll and a file version of 220.127.116.11 or lower.
To safeguard your update experience, we have applied a compatibility hold on Windows 10 devices with affected Conexant or Synaptics audio drivers installed from being offered Windows 10, version 2004 or Windows Server, version 2004 until the driver has been updated. If your organization is using Update Compliance, the safeguard ID is 25178825.
Workaround: To mitigate the safeguard, you might need to check with your device manufacturer (OEM) to see if an updated driver is available and install it. If updated drivers are not available for your device and you are offered Windows 10, version 2004 or Windows 10, version 20H2, a small number of devices might roll back to the previous version of Windows 10 when attempting to update. If this occurs, you should attempt to update to Windows 10, version 2004 or Windows 10, version 20H2 again.
Next steps: Microsoft and Synaptics are working on a resolution and will provide an update in an upcoming release. As of January 14, 2021, we are adjusting this safeguard to allow certain devices with the affected driver to update to Windows 10, version 2004 or Windows 10, version 20H2.
Note We recommend that you do not attempt to manually update using the Update now button or the Media Creation Tool until this issue has been resolved.
Errors or issues during or after updating devices with certain Conexant audio drivers
|Confirmed||N/A ||Last updated: 2021-01-05, 05:37 PT|
Opened: 2020-05-27, 12:20 PT
Synaptics and Microsoft have found incompatibility issues with certain versions of drivers for Conexant or Synaptics audio devices and Windows 10, version 2004 (the Windows 10 May 2020 Update). Windows 10 devices with affected Conexant or Synaptics audio drivers might receive a stop error with a blue screen during or after updating to Windows 10, version 2004. The affected driver will be named Conexant HDAudio Driver under Sound, video and game controllers in Device Manager and have versions 18.104.22.168, 22.214.171.124, or 126.96.36.199 through 8.66.89.00 for chdrt64.sys or chdrt32.sys.
To safeguard your update experience, we have applied a compatibility hold on Windows 10 devices with affected Conexant or Synaptics audio drivers installed from being offered Windows 10, version 2004 or Windows Server, version 2004 until the driver has been updated. If your organization is using Update Compliance, the safeguard IDs are 25702617, 25702660, 25702662, and 25702673.
Next steps: Microsoft and Synaptics are working on a resolution for safeguard IDs 25702617 and 25702660, and will provide an update in an upcoming release. Note We recommend that you do not attempt to manually update using the Update now button or the Media Creation Tool until this issue has been resolved.
Resolution: This issue was resolved for safeguard IDs 25702662 and 25702673. The safeguard hold has been removed for these safeguard IDs as of December 11, 2020. Please note, if there are no other safeguards that affect your device, it can take up to 48 hours before the update to Windows 10, version 2004 or Windows 10, version 20H2 is offered.