PnP interface notification

NTDEV
1

I want my driver to be notified whenever a serial port is being enabled.
I also need to know exactly which serial port is being enabled. Right
now, I’ve registered for PnP interface change notification on the COM
port interface, and I got notified all right. The problem is figuring
out *which* port caused the notification. In the callback routine, I
get the opaque symbolic link of the interface instance of that serial
port. On XP it looks like ??\Root#*PNP0501#PnPBIOS_14#{…}. I need
a way to go from there to the real device name, say \device\serial0 or
whatever. I’ve tried several things, the most promising being
ZwQuerySymbolicLinkObject. I give it the link, and it’s supposed to
give me the name of the device object. However, when I tried it, it
said my serial device is called \device\00000048. So, what’s the deal
with that? How can I get the device name that’s in the form of
\device\serialx, given the symbolic link to an instance of the COMPORT
interface? Any suggestion is much appreciated. Thanks!

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2

> a way to go from there to the real device name, say \device\serial0 or

I don’t think there is a notion of “real device names” in PnP. PnP device stacks are usually nameless. Device interface symlinks are
only names for them.
Serial stacks can have legacy names - but this is a legacy thing, intended for compatibility only.

If you want to number your devices - do it in your driver and write some kind of “get device number” or “get device GUID” IOCTL.

Max

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