Qualcomm EDL mode

Qualcomm EDL mode is a boot mode implemented in the boot rom of devices using Qualcomm SoCs, which includes features such as reading/writing partitions. It can be used for purposes such as unbricking hard-bricked devices, or flashing partitions on devices that lack fastboot mode or an equivalent.

Various clients for EDL exist, such as Qualcomm's own QFIL, qdl, or bkerler's 'edl'. Unless otherwise specified, the wiki will provide instructions using bkerler's client.

Dumping stock

The stock operating system of a device can be dumped with edl rl backup --skip=userdata --genxml. This will dump every partition other than userdata to a folder named backup, and generate an XML file.

(command adapted from here)

Bootloader unlocking

Some devices' bootloaders can be unlocked using EDL mode, by editing the devinfo partition.

First of all, devinfo must be dumped with edl r devinfo devinfo.bin.

Afterwards, the resulting devinfo.bin should be opened in a hex editor. The partition should have the magic ANDROID-BOOT! at the beginning, and optionally at other locations. Where it occurs, replace this:

41 4E 44 52 4F 49 44 2D 42 4F 4F 54 21 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

With this:

41 4E 44 52 4F 49 44 2D 42 4F 4F 54 21 00 00 00
01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00

Lastly, save the file, and flash it with edl w devinfo devinfo.bin.

(adapted from this XDA thread)