Suddenly two COM2 ?

[Thomas Johansen]

Hi

I have seen a strange problem on my XP boks.

I have written a device driver thats uses COM1. I therefore have created my
own group, so my driver is started after the Serial driver. The serial
driver is started with group Extended Base, so I have created my group just
after this on, in the ServiceGroupOrder list.

But suddenly I have to COM2 in my device manager (no COM1) and a warning in
my system log that says "Unable to create the symbolic link for
\Device\Serial0", event id 4. This has suddenly happen after a while and
many reboots/restarts.

This is what the PnP has detetcted:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_12\D
evice Parameters]
"DosDeviceName"="COM1"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_13]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_13\D
evice Parameters]
"DosDeviceName"="COM2"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_14]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_14\D
evice Parameters]
"DosDeviceName"="COM2"

This is what the serial driver used:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Serial]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Serial\Enum]
"0"="Root\\*PNP0501\\PnPBIOS_13"
"1"="Root\\*PNP0501\\PnPBIOS_14"

Any idea why the PnP suddenly has detected the same COM port again ??

After uninstalling COM2 and COM 2 from the device manger, PnP has now
installed COM1 and COM2

After re-install:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_13]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_13\D
evice Parameters]
"DosDeviceName"="COM1"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_14]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\*PNP0501\PnPBIOS_14\D
evice Parameters]
"DosDeviceName"="COM2"

Could it has something todo with my driver using serial device 0 ? To soon
usage of the port does something with PnP, or..... ???


Thomas

 

[Maxim S. Shatskih]

I have written a device driver thats uses COM1. I therefore have created my

own group, so my driver is started after the Serial driver.

Why not use PnP arrival notifications instead?

Also - if the device is PnP-enumerable from the COM port hardware, then use
SERENUM for it, like for serial mouse.