Bulb on Nikon D3100

[Disinterpreter]

Describe the bug

Hello! I haven't remote control, but I thought I could make a workaround with my laptop, but I found strange behavior.

I can't set the bulb.

Name the camera

Model                          Port
----------------------------------------------------------
Nikon DSC D3100 (PTP mode)     usb:000,004

libgphoto2 and gphoto2 version

gphoto2 2.5.28

Copyright (c) 2000-2021 Marcus Meissner and others

gphoto2 comes with NO WARRANTY, to the extent permitted by law. You may
redistribute copies of gphoto2 under the terms of the GNU General Public
License. For more information about these matters, see the files named COPYING.

This version of gphoto2 is using the following software versions and options:
gphoto2         2.5.28         clang, popt(m), exif, no cdk, no aa, jpeg, readline
libgphoto2      2.5.30         standard camlibs, clang, no ltdl, EXIF
libgphoto2_port 0.12.1         iolibs: disk ptpip serial usb1, clang, no ltdl, EXIF, USB, serial without locking

To Reproduce

1. Check /main/capturesettings/shutterspeed and find

   Choice: 51 30,0000s
   Choice: 52 Bulb

2. Set it gphoto2 --set-config /main/capturesettings/shutterspeed=52
3. Read an error

*** Error ***
The property 'Shutter Speed' / 0x500d was not set (0xa008: Shutter Speed Bulb)

configs.txt getconfig.txt shutterspeed52.txt

[msmeissn]

is the camera mode currently one that supports bulb, like e.g. TV, AV or M? (not sure if AUto or P support it)

[Disinterpreter]

is the camera mode currently one that supports bulb, like e.g. TV, AV or M? (not sure if AUto or P support it)

I used it only in Manual mode. And another modes aren't need me.

[Nic2012]

For my understanding Nikon allow only some cameras the bulb shooting while tethered:

Df, D3S, D4, D4S, D5, D500, D600, D610, D750, D800, D800E, D810, D810A, D850,  D5100, D5200, D5300, D5500, D5600, D7000, D7100, D7200, D7500, Z50, Z30, Z6, Z7