Node creation For real time devices

[Philipp Ittershagen]

Hi Manty!

On Fri, Apr 20, 2012 at 3:29 PM, manty kuma <mantykuma at gmail.com> wrote:
> Hi,
>
> I want to know how a node is created when a hardware is connected to the
> system.
>
> Information that I know :
> When a hardware is connected to the system, the device name is compared with
> the driver name, if it matches, then probe is called.
>
> Info i wish to know:
> At which point is the node created and who is creating it(In other words, i
> want to know where is mknod happening)?
>
> This one thing is bugging my mind from so many months. Please tell me
> programatically where is this happening. I will be very thankful.

Please correct me if I'm wrong, my understanding is this:

The hardware is connected and the corresponding subsystem or bus will
be notified (i.e. by interrupt of the device). The kernel then creates
an uevent and notifies the userspace part of udev (udevd) through a
netlink socket. The uevent is received by udevd and now udev can check
for rules to add the device node to /dev. That's when the creation and
naming of the device node happens.


Greetings,

  Philipp