I need to control mouse pointer of my computer screen using an external device.I just know i have to write a device driver for that device. It's a usb device.
Can anyone tell me how should i approach this problem ?
What are the modules and algorithms will be required for this?
I ll appreciate if you can provide some reference material?
Sorry for such trivial questions but am a newbie in Linux device driver area.
As guidance given by Mr. Stark which is essential before writing a module. As far as the problem of usb mouse driver you can check the following link. For the unknown USB device you can refer this link.
More links for usb mouse driver : link1 link2
Read Linux Device Drivers which tells you everything you need to know. Linux includes a USB mouse driver (I'm using one right now) which should be a good reference.
First, it can be useful to take a look to Linux USB. See writing USB device drivers.
Related
I want to read the GPS data from my android phone inside the kernel space. I want to write a device driver for my GPS and request data through it. But unlike external devices I could not find the Vendor Id and device Id of the GPS hardware or the SOC on which it is installed. Can someone help me with how to collect the details required for writing the driver?
Thanks.
You already have found one of many problems with SOC and device drivers. Therefore another approach is used in the linux kernel: Platform driver and Platform devices. You wont need any Vendor IDs and such stuff.
I recommend you to read some tutorials and get started with it:
Readme: https://www.kernel.org/doc/Documentation/driver-model/platform.txt
Code example for CAN: https://github.com/torvalds/linux/tree/master/drivers/net/can/ifi_canfd
Disscussion about difference: What is the difference between a Linux platform driver and normal device driver?
Sadly I am not able to answer your questions on how to get those id's.
I am learning to program a USB device (iBall 3.5g USB Dongle) using libusb.h header library.
Until now I am able to identify my device using the Vendor ID and also open the device for operation.
As a next step I would like to know the available commands (or the controls) for example : command to scan the surroundings for available GSM networks.
Obviously I will have to talk to the devices' firmware to extract the necessary information.
I tried to search for the technical datasheet for the 3g dongle, but couldn't find any.
The dongle is powered by a Qualcomm chip
Do you know any of the methods in which I can get the control commands for a usb device ?
Thanks in advance.
There is no simple procedure for figuring out what commands a USB device has. You need to use a combination of looking at the descriptors reported by the device, seeing if the device supports any particular USB device class, reading the USB specification, and maybe doing some reverse engineering using a protocol analyzer.
A good first step would be for you to use lsusb -v to print human-readable descriptions of the device's USB descriptors.
I am designing a USB keyboard with special capabilities. What information can such a HID device receive from the host?
Can I via USB:
Read data from a form on the screen?
Find out what OS the user is on?
Find out if there's been an error message?
Even 'know' what's going on visually on the screen, i.e. what program is selected or whether the program is windowed or fullscreen?
Thank you!
The device can't get any of this information from a standard driver that the operating system supplies because that would be a security issue. It can receive any information that your own driver or application sends it. There are many ways to communicate with it - your device could present multiple interfaces (which will appear as separate devices), multiple endpoints, or use the control channel. You will definitely need to study the spec, and I also found this tutorial helpful.
I have done something similar and used the control channel to exchange feature data with a Windows application (over the standard Windows driver). On Windows, the API calls are HidD_SetFeature() and HidD_GetFeature().
On the device side, my hardware ran embedded Linux and I used the GadgetFS library to create a user-mode driver - much easier to debug than a kernel driver.
As others have said, you'll run into issues if you try this with a normal HID. However, there is a project called the USB Rubber Ducky. From their description:
The USB Rubber Ducky isn't your ordinary HID (Human Interface Device).
Coupled with a powerful 60 MHz 32-bit processor and a simple scripting language
The USB Rubber Ducky looks like a usb-device and is recognized as a HID, but is programmable. You can make a small script that will be typed onto the screen which will allow you to performs the queries you seek.
With the USB Rubber Ducky you can:
Read data from a form on the screen? Yes
Find out what OS the user is on? Yes
Find out if there's been an error message? Yes
Even 'know' what's going on visually on the screen, i.e. what program is selected or whether the program is windowed or fullscreen? Yes
If you aren't hoping to buy this device, at least their firmware is on github so it can provide you a starting point
I am trying to find out a high-level overview of how the USB storage driver works in Linux. I'm looking for a simple article or even a picture/flowchart describing how it works.
Basically, I'm looking to get these questions answered:
When you plug the device into your computer, what happens? Is there a daemon that picks up on it, or does the event trigger an interrupt somewhere? Does the core USB driver read information about the device before passing control over to the USB storage driver? How does it decide what type of device it is? How does the device get mounted, and what allows it to communicate with the computer's filesystem? When I copy a file, what does the data flow look like in the kernel?
I hope the question isn't too vague - I tried Google to no avail, so I'm wondering if anyone knows any articles or diagrams that can explain this, or perhaps if they can explain it themselves without too much effort. Thanks.
No, it is a very good question.
The block writing is going in linux with the block device layer. The filesystems are working with this block dev layer.
If this layer wants to write something out, says it to the driver of the usb master device. This driver is talking with the usb controller chip of the motherboard.
This chip is very simple: the usb is practically a serial port, with a lot of extensions, mainly targeting the autoconfiguration and the power management. But basically, you can write out bytes, and read in bytes.
Your questions:
When you plug the device into your computer, what happens? Is there a daemon that picks up on it, or does the event trigger an interrupt somewhere?
The device (usb slave) says the master (in the motherboard): "I am here". The usb controller chip gets the message and says it to the kernel (normally) with an interrupt. The kernel reinitializes and rescans the usb bus, and says the udev: "here is a new 1234:5678 usb device on the usb tree 1.3.5"
"How does it decide what type of device it is?"
Usb devices have a vendor and model id, and they can say this on ask. Google for "usb ids".
"How does the device get mounted, and what allows it to communicate with the computer's filesystem?"
The kernel only loads the driver and says the udev (which is in userspace): "Here is a new block device on device number 22:16". From this, udev tries to mount this with some userspace daemon, it is already distribution-dependant.
Please help me, How can i get the pre notifcation of an inserted usb device, before enumeration starts in linux ?
You can use libudev to get notifications of added/removed devices.
Here's a tutorial for libudev. You can also use the code here to get started.
There's also libusb available for usb events/manipulation.