Varos Port Devices Driver

For most devices, the Ports device setup class and the Serial function driver provide the functionality required to operate serial ports and COM ports. To install serial ports and COM ports using these system-supplied components, do the following. Virtual COM port (VCP) drivers cause the USB device to appear as an additional COM port available to the PC. Application software can access the USB device in the This page contains the VCP drivers currently available for FTDI devices. For D2XX Direct drivers, please click here.

Improvements and fixes

This update includes a fix for an incorrect device driver (β€œMicrosoft – WPD – 2/22/2016 12:00:00 AM - 5.2.5326.4762”) that was released by a third-party on March 8, 2017 that affected a small group of users with USB connected phones or other media devices that rely on Media Transfer Protocol (MTP). If the driver is on your system, when any of these devices are connected, Windows will try to install this driver. These devices will not be connected until the driver is removed. This incorrect driver was removed from Windows Update the same day, but it may have been downloaded to your computer. After installing this update the incorrect driver will be removed.

How to get this update

This update will be downloaded and installed automatically from Windows Update. To get the stand-alone package for this update, go to the Microsoft Update Catalog website.

If you are not able to connect your phone or media device via USB and are not running one of these Windows versions, you can still remove this driver using the process described here:

The 2.6 kernel contains a long list of changes which affect device driverwriters. As part of the task of porting the Linux DeviceDrivers sample code to 2.6, your humble LWN Kernel Page author isproducing a set of articles describing the changes which must be made.The articles are Kernel Page as they are written; they will also becollected here. With luck, this page will be a useful reference for thosewho must port drivers to the new kernel.

The creation of these articles is funded by subscribers. Drivers scantron cameras software. If youfind this material useful, please consider subscribing to LWN to helpensure that more of it gets written.

Except when otherwise specified, all of the articles below are written byLWN editor Jonathan Corbet. The date and kernel version attached to eacharticle notes when the article was last updated.

Recent changes

The most recent changes to this series are:
  • (April 28, 2004) The Workqueue Interface updated to include create_singlethread_workqueue(), which was merged in 2.6.6.
  • (January 6, 2004) Supporting mmap() and Dealing with interrupts have been updated to reflect API changes in 2.6.1.
  • (November 25, 2003) The entire set of articles has been updated to reflect the 2.6.0-test10 kernel.

Getting started

Porting 'hello world' (February, 2003); whichcovers the changes required to update the simplest possible module to the 2.5 kernel.

Compiling external modules (November, 2003; 2.6.0-test9); how to build modules with the new module loader and kernel buildscheme.

More module changes (November, 2003,2.6.0-test9) covers other changes to the module loading subsystem, including module parameters, use countmanagement, exporting symbols, and more.

Miscellaneous changes is a collection pointfor changes which are too small to justify their own article. Currentlycovered topics include kdev_t, designated initializers, andmin() and max(). It was last updated on November 3,2003 (2.6.0-test9).

Support interfaces

Char drivers and large dev_t (November 2003,2.6.0-test9); registration and management of char drivers in the new, large dev_t environment.

The seq_file interface (September 2003; 2.6.0-test6); theeasy way to implement virtual files correctly. A standalone example moduleis provided to demonstrate the use of this interface.

Low-level memory allocation (November, 2003;2.6.0-test9); changes to functions for allocating chunks of memory and pages, anda description of the new mempool interface.

Per-CPU variables (November, 2003; 2.6.0-test9); the 2.6interface for maintaining per-CPU data structures.

Timekeeping changes (November, 2003; 2.6.0-test9);changes to how the kernel manages time and time-related events.

The workqueue interface (April, 2004; 2.6.6-rc3); adescription of the new deferred execution mechanism which replaces taskqueues (and bottom halves in general).

Creating virtual filesystems with libfs(November, 2003; 2.6.0-test9). This article, which looks at how a kernel module cancreate its own virtual filesystem, predates the driver porting series butfits in well with it.

DMA Changes (November, 2003, 2.6.0-test9); changesto the DMA support layer. There is also a quick reference page for thenew generic DMA API.

Varos Port Devices Drivers

Sleeping and mutual exclusion

Mutual exclusion with seqlocks (November,2003, 2.6.0-test9); a description of how to use the seqlock (formerly frlock) capabilitywhich was merged into 2.5.60.

The preemptible kernel (November, 2003; 2.6.0-test9); alook at how kernel preemption affects driver code and what can be done towork safely in the preemptible environment.

Sleeping and waking up (November, 2003; 2.6.0-test9); newways of putting processes to sleep with better performance and without raceconditions.

Completion events (November, 2003; 2.6.0-test9);documentation for the completion event mechanism.

Using read-copy-update (November, 2003; 2.6.0-test9);working with the read-copy-update mutual exclusion scheme.

Varos Port Devices driver

Advanced driver tasks

Dealing with interrupts (January, 2004; 2.6.1-rc2);interrupt handling changes which are visible to device drivers.

Supporting asynchronous I/O (November, 2003;2.6.0-test9);how to write drivers which support the 2.6 asynchronous I/O interface.

Network drivers (November 2003, 2.6.0-test9); portingnetwork drivers, with an emphasis on the new dynamic net_deviceallocation functions and NAPI support.

USB driver API changes (July 2003; 2.5.75);how USB drivers have changed in the 2.5 development series. This articlewas contributed by USB maintainer Greg Kroah-Hartman.

Block drivers

Block layer overview (November, 2003; 2.6.0-test9). Theblock layer has seen extensive changes in the 2.5 development series; thisarticle gives an overview of what has been done while deferring the detailsfor subsequent articles.

A simple block driver (November, 2003; 2.6.0-test9); thisarticle presents the simplest possible block driver (a basic ramdiskimplementation) with discussion of how the basic block interfaces havechanged in 2.6. Full source to a working driver is included.

The gendisk interface (November, 2003; 2.6.0-test9); how towork with the new generic disk interface, which takes on a rather largerrole in 2.6.

The BIO structure (November, 2003; 2.6.0-test9); the newlow-level structure representing block I/O operations.

Request queues I (November, 2003; 2.6.0-test9); the basicsof block request queues in 2.6, including request processing, requestpreparation control, and DMA support.

Request queues II (November, 2003, 2.6.0-test9); advancedrequest queue topics, including command preparation, tagged commandqueueing, and the 'make request' mode of operation.

Memory management

Supporting mmap() (January, 2004 - 2.6.1-rc2);changes in how device drivers support the mmap() system call.

Zero-copy user-space access (November, 2003 -2.6.0-test9); how to get direct-access to user space to perform zero-copy I/O.If you used the kiobuf interface for this purpose in 2.4, you'llwant to look here for the 2.6 equivalent.

Atomic kmaps (November, 2003; 2.6.0-test9); quickaccess to high-memory via kmap_atomic().

Device model

A device model overview (November, 2003; 2.6.0-test10);an introductory look at the Linux device model and sysfs, with definitionsof some commonly encountered terms.

The zen of kobjects (October, 2003;2.6.0-test6); an attempt to demystify the kobject abstraction and its usein the kernel.

kobjects and sysfs (October, 2003;2.6.0-test8); a description of the interaction between the kobject type andits representation in sysfs.

kobjects and hotplug events (October, 2003;2.6.0-test6); an explanation of the kset hotplug operations and how theycan be used to control how hotplug events are reported to user space. Thisarticle was written by Greg Kroah-Hartman.

Examining a kobject hierarchy (October,2003; 2.6.0-test9); a visual exploration of the device model datastructures behind /sys/block.

Varos Port Devices Driver

Device classes (November, 2003; 2.6.0-test10); howthe device class mechanism works.

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