Qualcomm - Qcser.inf

What is qcser.inf?

• Verdict: Legitimate, trusted Microsoft/WinQual driver file – not malware.
• Full name: Qualcomm Serial Device Driver Setup Information file.
• Purpose: Installs USB serial drivers for Qualcomm-based mobile devices (smartphones, tablets, modems, IoT modules) when connected to a Windows PC, typically for diagnostics, flashing firmware, or debugging (QDLoader/HS-USB mode).
• Signed by: Microsoft Windows Hardware Compatibility Publisher (or Qualcomm).
• Typical location: C:\Windows\INF\ (and C:\Windows\System32\drivers\ for the .sys file).

Troubleshooting Common Error Codes

6. Hardware IDs Typically Found in qcser.inf

The file contains strings like:

USB\VID_05C6&PID_9001
USB\VID_05C6&PID_9002
USB\VID_05C6&PID_9091
USB\VID_05C6&PID_9025

• VID_05C6 = Qualcomm’s USB Vendor ID
• PID_*** = Product ID for different serial functions

The Difference Between qcser.inf, qcmdm.inf, and qcaux.inf

Qualcomm uses a family of INFs for different interfaces: qualcomm qcser.inf

| INF File | Purpose | Virtual Port Type | | :--- | :--- | :--- | | qcser.inf | Generic serial/Diagnostic (Diag) | COMx | | qcmdm.inf | Modem command channel (AT commands) | COMx (different PID/VID) | | qcaux.inf | Auxiliary logging (GPS NMEA, audio debug) | COMx | What is qcser

When you install the full Qualcomm driver package, all three apply to the same physical device, producing multiple COM ports. Troubleshooting Common Error Codes 6

2. Associated Software

This file is typically bundled with driver packages for:

• HP lt4112 LTE/EV-DO/HSPA+ WWAN Module
• HP lt4111 LTE/EV-DO/HSPA+ WWAN Module
• Dell Wireless 5570 HSPA+ (42 Mbps) Mobile Broadband Card
• Various unbranded Qualcomm Gobi 2000/3000/4000/5000 chipsets.