Hello! I have a question regardind dbus on the current(2.6.35) kernel. Is dbus a way of communication between kernel and user space? I can figure it out by myself. For exemple if you make use of the usb driver(inserting something like a usb flash pen) and monitoring the activity of the dbus(dbus-monitor) the answer might be yes. But in the source code(usb-skeleton.c and the driver for gadgets there's no sign of dbus). Dbus.h is not to be found in the kernel tree. Thank you very much. Sorry if i've got this wrong but i am kind of a noob on device drivers and dbus!
A:
D-Bus (or "daemon bus") is a means of communication between processes (inter-process communication or IPC for short) on Linux/Unix based systems.
It lets processes expose a "D-Bus service" with methods that clients can call. These methods usually map to real methods written in some programming language. D-Bus is language-independent, but most toolkits have some library to make it easier to use - e.g. QtDbus.
It is in no way related to the kernel or drivers, but of course no one prevents a driver from also having a D-Bus service if they want to. (This could be useful in some cases.)
Venemo
2010-09-04 18:43:39
A:
D-Bus is for user space applications to communicate with one another.
If you want to speak to communicate with a device driver you want to use either IOCTLs, netlink or create a new syscall. I've created netlink code in the past to speak to a special networking card, and it was relatively easy to do. Using the ioctl is also quite easy but you are limited by how much information you can/should pass via it.
If you are curious how dbus relates to a USB device being inserted, I think it is something like this:
Kernel -> udev -> udisks (formally DeviceKit) -> dbus -> any dbus application interested in disk events.
bramp
2010-09-04 18:43:52
For work i have to provide a "test" that will have to "demonstrate" that Dbus is a way of communication between user and kernel space. Any suggestions?(amoung other tests like dbus is compliant with POSIX, etc etc...)
mannox
2010-09-04 19:01:14
Well you'll going to have to write some kind of daemon that communicates with the kernel via an existing kernel-user IPC (such as the ones I listed) and hook this daemon up to D-Bus.
bramp
2010-09-05 14:08:05