for Linux, there is a nifty little library called xbindkeys that (surprise) binds commands of your choice to certain key combinations.
I am looking for something similar, except for a system hardware event. When I plug in my headphones to the output jack on my computer, I would like to be able to call a program. It would also be nice to be able to bind to the event when I un-plug my headphones.
Does anybody know if this is possible? Maybe through some cool Python X11 library?
Thanks in advance.
EDIT: Found the API for the jack abstraction layer: http://www.alsa-project.org/~tiwai/alsa-driver-api/ch06s02.html
Sadly, this only allows for polling of the device, not an event handler.
You probably want to use udev for this. I haven't used libudev, but here's something I found:
libudev - Monitoring Interface
libudev also provides a monitoring interface. The monitoring interface
will report events to the application when the status of a device
changes. This is useful for receiving notification when devices are
connected or disconnected from the system.
The actions are returned as the following strings:
add - Device is connected to the system
remove - Device is disconnected from the system
change - Something about the device changed
move - Device node was moved, renamed, or re-parented
That article goes on to show how it obtains a file descriptor via udev_monitor_get_fd, which it later monitors via select.
Most modern Linux desktops (notably Gnome and KDE) use "DBus".
DBus, in turn, utilizes HAL (older) and/or udev (newer).
Here are a couple of links that explain further:
https://www.linux.com/news/hardware/peripherals/180950-udev
http://w3.linux-magazine.com/issue/71/Dynamic_Device_Management_in%20Udev.pdf
http://dbus.freedesktop.org/doc/dbus-tutorial.html
Related
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 want to scan the signal strength received from 3 AP.
I would be happy if that could happen every 300ms (max.500ms). I flashed OpenWRT on the routers.
I was seeking for a good tool to do that.
First I found iwconfig which worked, but only with networks that I was connected to. So I used iwlist (iw didn't work- maybe I need to update it?). Do you know how accurate is the output of it? Can I trust it?
After that, I came across the IOCTL. It looks really powerful* and professional. But is the output from getting the signal stregnth from a WIFI more reliable than the simple method like iwlist/iw?
*even too much powerful as I failed to compile any program I wrote using it
If you want to determine the signal strength of WLAN access points to which you are not connected, scanning is the right way.
The scanning is performed by the wireless network card with much or little "help" from the driver, depending on the design of the wireless card. There are cards (chipsets, to be more specific) that have their own processor and run their own firmware code independently from the host computer. On the other end, there are "stupid" cards where the driver on the host computer does most of the work.
Between the driver and the rest of the operating system, there is an interface (API) for sending commands to the driver and reading back information in a standardized way. With Linux, there are at least two different APIs. The older one is named Wireless Extensions, and the newer one is named cfg80211. Normally, a driver supports only one of the APIs. Most current drivers use cfg80211, but there may be older drivers that still use Wireless Extensions.
For each of the two APIs, there's a user-space tool (or family of tools) to use it. For Wireless Extensions, there is iwconfig (and iwlist, iwpriv etc.) For cfg80211, there is just iw.
So, the questions about the right tool depends on what API the wireless driver uses. To add confusion ;-), cfg80211 does some emulation which allows you to perform some Wireless Extension calls to drivers that use the newer cfg80211 API.
Regarding your questions about ioctl(): This is a generic method for communication between user-space and kernel-space in Unix operating systems. The old Wireless Extensions API uses ioctl(). The newer cfg80211 API does not use an ioctl()-based interface, but uses nl80211 instead.
To sum it up: whether to use iw/cfg80211/nl80211 or iwconfig/Wireless Extensions/ioctl depends on the driver or your wireless card.
Regarding your desired scanning interval, I would say that 300ms is rather short. This is because for a useful scan, the client needs to leave its current channel for a short time, switch to another channel and listen to signals from other access points on this channel. Since leaving its channel interrupts communication, these off-channel times are usually kept short and are carried out infrequently.
Calling iw <dev> scan or iwlist <dev> scan, respectively, will not necessarily cause a new scan, but may return an old (cached) list of access points. Depending on your wireless card/driver it may be (im)possible to enforce a new scan.
I need to display the status of the ethernet connection (eth0) on the GUI, i.e. is the link up or not.
I have a Davicom DM9000 PHY.
I know there are various ways to skin this cat, like parsing ifconfig, polling /sys/class/net/eth0/operstate, etc.
However, as I will need to monitor other devices also, like USB, I would like to use libudev for this as a more generic implementation.
Furthermore, I would like to use the monitor mechanism (using a select() ) and in doing so prevent having to poll.
I have wrapped the libudev functionality in a Qt class and intend on using signal/slot mechanisms to indicate events to my program.
Problem is, I can't seem to generate UDEV events from eth0 no matter what.
I have also tried using
udevadm monitor
but no events either when unplugging my ethernet cable.
I don't think my code is too far off, because I am able to generate events for USB (hidraw) devices by unplugging my keyboard, for example.
Also, I am able to see eth0's attributes using the libudev enumerate mechanism (but this is a polling process)
My question - is this possible, i.e. to use libudev's udev_monitor functions to catch events on eth0?
Sorry for the long post.
Have already looked at D-bus? Via D-Bus and underlying services you can get all the info you need. See this a little bit outdated article to understand the concept. See Qt/D-Bus documentation.
I have to simulate a USB Device for automation and testing purposes (in Linux). Original driver/application for this device uses “libusb” to communicate with it.
I don’t have much experience in Linux and Simulation, after some searching I have understood that I need to write a kernel level driver and an application in user-space to simulate that device. Is this right? If Yes, How can this be done?
Thanks in Advance.
Finally implemented it by modifying "libusb", modified it to send and receive usb transfers from message queue instead of usbfs. Programmed my simulator to create libsub type transfers and send/receive them using message queues as well.
Simulator now interprets the incoming transfers and sends it to a command parser, which sends request/message to automation system using sockets in a specific format. Automation system sends it's instruction by sending to command parser using socket. This socket invokes method specific to each request in simulator, Now simulator forms an appropriate transfer structure and passes to device plugin (via libusb) through message queue.
I think what you're looking for would be called a virtual USB device. Currently there is nothing in standard Kernel.Some virtual machine provides USB emulation.e.g. KVM provides USB emulation. There is framework gadget in which might look for your solution.
Or find something in Linux USB project
Thanks,
Abhijeet
The usb-vhci project could be of use if you want the device to be presented to the kernel in the same way as real hardware.
Is it possible to make a computer behave as a bluetooth HID device? That is, given a local machine with a standard USB keyboard plugged into it, other devices could discover this machine and use it as a bluetooth keyboard.
I'd like to create a linux or OS X application (or use an existing one, though I've found none) which can behave as described above, but I'm not sure where to start, or if it's even possible.
So:
Is what I'm describing possible?
Are there any existing applications that do what I describe?
If no application already exists (I'm assuming not), are there bluetooth libraries or bindings that will help? (I'm pretty comfortable using most of today's popular languages, so I'd prefer a library most directly suited to the task, so long as it's available in linux or OS X.)
Failing any of the above, the bluetooth spec looks pretty dense. Are there specific guides or other starting points applicable to the problem at hand that I can read?
I realize that such an application would most likely need to steal the normal keyboard input, possibly providing some KVM-like hotkey for switching between providing input to the host operating system and sending the input over bluetooth to the connected device, but I'm considering that problem to be outside the scope of this question.
It is definitely possible on Linux. Some time ago I found this project:
http://nohands.sourceforge.net/index.html
They emulate a full-blown headset with audio and keyboard controls on the Linux bluetooth stack. If they can emulate something like that, you would probably be able to emulate something simpler like a keyboard.
It is possible, however I don't think I'll be able explain it very well and I don't know the entire answer. A BT HID device works as a server and waits for connections to come to it. In linux, using the bluez stack, first you would have to advertise the HID service for other devices to see. I think you do that using the sdp.h and sdp-lib.h header files(the second header maybe called something else, I'm on a windows computer and can't check). So you would have to add the HID service record to you computer for other devices to see it. You would have to create a program that first adds this service to the record, then waits for other devices to connect, then handle the pairing process, Bluez might handle this for you, or you might have to do some things to it, I'm not quite sure. You should also read the Bluetooth HID Spec found at the http://www.bluetooth.com/English/Technology/Building/Pages/Specification.aspx site. This document contains the details of the SDP record relevant to HID. Also the book Bluetooth essentials for programmers is pretty good to introduce you into bluetooth programming
I would like to have given a more concise answer, with more detail, but that's all I know ATM. I am also trying do something similar, but spare time is so hard to find ;) I'm also not on my Linux box and can't check all the details. If your are still interested, let me know and i'll try to expand my answer.
I don't know if this is helpful, nor if it is still alive and working, but perhaps you could try this link.
Another one that might or might not be helpful in some way is remuco, but I don't know if they are using a Bluetooth HID profile.
It is indeed entirely possible with Linux and Bluez. See: https://github.com/lkundrak/virtkbd/blob/master/btkbdd.pod
Try Across, unfortuantly for me my phone was lacking support.