Introduction
CSR is often called “driverless DFU” and is used only by BlueCore chips from Cambridge Silicon Radio (now owned by Qualcomm). The driverless just means that it’s DFU like, and is routed over HID.
CSR is a ODM that makes most of the Bluetooth audio chips in vendor hardware. The hardware vendor can enable or disable features on the CSR microcontroller depending on licensing options (for instance echo cancellation), and there’s even a little virtual machine to do simple vendor-specific things.
All the CSR chips are updatable in-field, and most vendors issue updates to fix sound quality issues or to add support for new protocols or devices.
Firmware Format
The daemon will decompress the cabinet archive and extract a firmware blob in DFU file format.
This plugin supports the following protocol ID:
com.qualcomm.dfu
GUID Generation
These devices use the standard USB DeviceInstanceId values, e.g.
USB\VID_0A12&PID_1337&REV_2520USB\VID_0A12&PID_1337USB\VID_0A12
Update Behavior
A DFU device usually presents in runtime mode (or with no interfaces defined), but if the user puts the device into bootloader mode using a physical button it then enumerates with a HID descriptor. On attach the device returns to runtime mode which may mean the device “goes away”.
For this reason the REPLUG_MATCH_GUID internal device flag is used so that
the bootloader and runtime modes are treated as the same device.
Vendor ID Security
The vendor ID is set from the USB vendor, in this instance set to USB:0x0A12
External Interface Access
This plugin requires read/write access to /dev/bus/usb.