syfs question

[Sadanand Warrier]

If I call device_create with a existing class the device lands up in
/sys/devices/virtual.  Using device_add I could populate the parent of the
device and leave the class empty or provide a class and get the device to
be created in the parent directory.

What exactly is the significance of the" /sys/devices/virtual"  directory?
Is this meant to carry devices of a specific type say something that is
divorced from actual hardware?

Secondly a device created under /sys/devices/virtual has a uevent file that
is populated like this.

-bash-4.2$ cat uevent
MAJOR=13
MINOR=63
DEVNAME=input/mice
-bash-4.2$

A device in a specific PCI slot has something like this instead..
-bash-4.2$ cat
/sys/devices/pci0000:00/0000:00:02.2/0000:03:00.3/net/eth1/uevent
INTERFACE=eth1
IFINDEX=3

How is this file populated? Is it done by udev or is this done via a kernel
call?

Thanks

S
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