QMI-RIL¶

This page covers development efforts to create a Radio Interface Layer (RIL) for modems that use the Qualcomm MSM Interface (QMI) protocol. The work is currently carried out for the Galaxy S 3 4G (I9305) which has a Qualcomm MDM9615 modem. The Galaxy Note 2 4G (t0lte) uses the same modem and this device could be supported as well in Replicant when the QMI-RIL is ready. We will hopefully identify further candidates that have an isolated modem using the QMI protocol and for which Replicant support could be added. Among the non-Android devices, the iPhone 5 is one that uses the MDM9615 modem as well.

Modem boot¶

When the MDM9615 modem is activated, it first boots into a download mode. There, firmware, bootloaders and EFS files are uploaded to the modem via a serial interface. The used protocol is called SAHARA and it is a proprietary protocol developed by Qualcomm. The protocol covers various functionalities. We will likely only need to implement a very small subset that is responsible for transferring firmware and other files to the modem and possibly synchronising changes to EFS files with the filesystem.

Qualcomm provides the proprietary tool kickstart for uploading the files to the modem. It is run by the daemon qcks. The options qcks supplies to kickstart show which files need to be transferred:

/system/bin/ks -v  -w /data/cp_log/ -p /dev/ttyUSB0 -f 0 -r 21 -s 2:/firmware/image/amss.mbn -s 6:/firmware/image/apps.mbn -s 8:/firmware/image/dsp1.mbn -s 11:/firmware/image/osbl.mbn -s 12:/firmware/image/dsp2.mbn -s 21:/firmware/image/sbl1.mbn -s 22:/firmware/image/sbl2.mbn -s 23:/firmware/image/rpm.mbn -s 28:/firmware/image/dsp3.mbn -s 16:/tombstones/qcks/efs1.bin -s 17:/tombstones/qcks/efs2.bin -s 20:/tombstones/qcks/efs3.bin -s 29:/tombstones/qcks/acdb.bin

Logcat and dmesg output of the upload: ks_logcat, ks_dmesg

libopenpst can be used as a reference to implement the file upload and as documentation about the protocol. The kernel itself can be checked for the different boot modes.

QMI protocol¶

libqmi is a library that implements the QMI protocol and it will be used for implementing the RIL. libqmi needs the cdc-wdm and qmi_wwan kernel drivers for communicating with the modem. These are backported to the smdk4412 kernel on the qmi branch. The branch is not yet merged into the replicant-6.0 branch because one commit sets SELinux to permissive. This is more convenient for development.