The ath11k Driver¶
This is the device driver that works with the Qualcomm WCN6750 that provides support for the non cellular radio traffice. There are multiple layers of APIs and data protocols used to support the radio devices. The ath11k driver code is copyrighted by both Qualcomm and the Linux Foundation and uses a BSD-3-Clause-Clear license. This is the same driver source as used by the Linux kernel as well. The layers in order are:
- Android kernel
- WMA - Wireless Management Agent (WMA)
- WMI - Wireless Module Interface
- HTC - Host-Target Communication
- HIF - Host interconnect Framework
- PCI - PCIe
- CE - Copy Engine
Qualcomm Open Source Release¶
Qualcomm has released code for the WCN6750 that handles the higher level protocols, Wireless Module Interface (WMI) and Wireless Management Agent (WMA), and the Host Device Driver (HDD). The kernel module's source code for that can be found here. It is copyrighted by both Qualcomm and the Linux Foundation and uses a ISC license.
Host Device Driver (HDD)¶
This is the interface between the lower level code in the WMA and the kernel device driver, with the source code in the qcacld-3.0/core/hdd directory. This is a higher level interface than anything this project needs to look into in any detail.
Wireless Management Agent (WMA)¶
This is the interface for higher level commands from the HDD for the WMI, with the source code in the qcacld-3.0/core/wma directory. This is a higher level interface than anything this project needs to look into in any detail.
Wireless Module Interface (WMI)¶
This is primary interface between the driver and the blob. This is an bi-directional asynchronus command layer for controlling the radio device. The source for this is in two directories qcacld-3.0/components/wmi and qca-wifi-host-cmn/wmi. There is also a file in the ath11k driver directory, ath11k/wmi.c and ath11k/wmi.h that uses the qca library. This defines the commands used in the data stream between the kernel and the hardware.
This is a good layer to document the API, and get some insight into what a reimplemented blob would need to support. This uses the HTC for the transport layer to the blob.
Host-Target Communication (HTC)¶
This sends or recieves the commands from the WMI. This doesn't directly talk to the blob, it uses the HIF for the actual data exchange. The source code for this is in two directories. The primary one is in the qca library from Qualcomm, qca-wifi-host-cmn/htc, and the ath11k driver has an htc.c file that uses this library.
Host interconnect Framework (HIF)¶
Abstracts the access to different bus types. Currently only supports PCI, but it’s easy to add different bus types. The source code for this is in two directories. The primary one is in the qca library from Qualcomm, qca-wifi-host-cmn/hif. The ath11k driver has a file ath11k/hif.h that connects the library to the driver.
PCIe Interface¶
This is the lowest level API for communicating with the hardware. The primary source code in in the qca library in the qca-wifi-host-cmn/hif/src/ipcie and qca-wifi-host-cmn/hif/src/pcie directories. The ath11k driver has a file ath11k/pci.c that connects the library to the driver.
The Copy Engine¶
Communication with the blob is done using the Copy Engine, which is a bi-directional ring of DMA buffers. The source file that defines the data structures is in the ath/ath11k/core.h file. The 3 data structures of interest are These are ath11k_ce, ath11k_ce_pipe, ath11k_ce_ring.