[Nexus 5 General] bitdomo:
Yes I forgot to say that :).

People who killed their bootloaders get Qualcomm HS-USB QDloader 9008 device (without drivers it is QHSUSB_BULK) when they connect their devices to the PC. If they try to enter Download mode they get a black screen as well, but on the pc LGE androidnet serial usb port device comes up. Atleast two out of two people's phone do these symptoms. I don't know what's with the others. LGE androidnet serial usb port device is used to setup CDMA networks on nexus 5, there is a thread about it somewhere. So in short LGE androidnet serial usb port is useless for LG flashtool.

I started an investigation on LGE androidnet serial usb port device to figure out why this comes up for that two people. I found out when you try to enter to Download mode then the phone boots up the LAF image, which is a kernel image like recovery.img or boot.img. I extracted the ramdisk of the LAF (it is on the laf partition) and I found this file init.laf.usb.rc.

# init.laf.usb.rc

# it can run as user cable
on property:ro.boot.laf=USER
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 1004
write /sys/class/android_usb/android0/idProduct 6000
write /sys/class/android_usb/android0/bDeviceClass 2
write /sys/class/android_usb/android0/bDeviceSubClass 0
write /sys/class/android_usb/android0/bDeviceProtocol 0
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions acm,laf
write /sys/class/android_usb/android0/enable 1

# it can run as user cable for PID of verizon
on property:ro.boot.laf=VUSER
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 1004
write /sys/class/android_usb/android0/idProduct 6246
write /sys/class/android_usb/android0/bDeviceClass 239
write /sys/class/android_usb/android0/bDeviceSubClass 2
write /sys/class/android_usb/android0/bDeviceProtocol 1
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions acm,laf,ecm
write /sys/class/android_usb/android0/enable 1

# it can run as factory cable(910K USB cable)
on property:ro.boot.laf=910K
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 1004
write /sys/class/android_usb/android0/idProduct 6000
write /sys/class/android_usb/android0/bDeviceClass 2
write /sys/class/android_usb/android0/bDeviceSubClass 0
write /sys/class/android_usb/android0/bDeviceProtocol 0
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions acm,laf
write /sys/class/android_usb/android0/enable 1

# it can run as factory cable(56K USB cable)
on property:ro.boot.laf=56K
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 1004
write /sys/class/android_usb/android0/idProduct 6000
write /sys/class/android_usb/android0/bDeviceClass 2
write /sys/class/android_usb/android0/bDeviceSubClass 0
write /sys/class/android_usb/android0/bDeviceProtocol 0
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions acm,laf
write /sys/class/android_usb/android0/enable 1

# it can run as factory cable(130K USB cable)
on property:ro.boot.laf=130K
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 1004
write /sys/class/android_usb/android0/idProduct 6000
write /sys/class/android_usb/android0/bDeviceClass 2
write /sys/class/android_usb/android0/bDeviceSubClass 0
write /sys/class/android_usb/android0/bDeviceProtocol 0
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions acm,laf
write /sys/class/android_usb/android0/enable 1

# it can run as user cable for QCT PID
on property:ro.boot.laf=QCOM
wait /sys/class/android_usb/android0/enable
write /sys/class/android_usb/android0/enable 0
write /sys/class/android_usb/android0/idVendor 05C6
write /sys/class/android_usb/android0/idProduct 903A
write /sys/class/android_usb/android0/f_acm/acm_transports tty
write /sys/class/android_usb/android0/f_diag/clients diag
write /sys/class/android_usb/android0/functions mtp,laf
write /sys/class/android_usb/android0/enable 1

So, for some reasone for those two guys the laf runs the "on property:ro.boot.laf=QCOM" lines and not the "on property:ro.boot.laf=USER" lines. In the comments you can see both of this mode triggered by "user" cable. I think "user" cable means the normal usb cable. There are 3 more "modes" for 56k, 130k, 910k cables all of these three are identical with "on property:ro.boot.laf=USER" settings. Maybe if that two people get or make one of those cable then they can avoid to get the "on property:ro.boot.laf=QCOM" lines run.

I attached the ramdisk to this post.