README: Update for Monterey and new MBPs

- Indicate how to get the serial device on Monterey
- Document the location of the debug port on 14"/16" MBPs

Signed-off-by: Vincent Duvert <[email protected]>

Author: rickmark

README.md

@@ -19,13 +19,52 @@ Thanks to t8012.dev and mrarm for assistance with the VDM and Ace2 host interfac
 
 The documentation of the ACE and its USB-PD VPDs is here https://blog.t8012.dev/ace-part-1/
 
+## Note about macOS 12
+
+To have access to the serial console device on macOS Monterey (12), you need to disable the `AppleSerialShim` extension.
+
+**Note:** This requires downgrading the system security and may cause problems with upgrades. Use it at your own risk!
+
+Start by generating a new kernel cache, without the `AppleSerialShim` extension:
+
+```
+sudo kmutil create -n boot -a arm64e -B /Library/KernelCollections/kc.noshim.macho -V release  -k /System/Library/Kernels/kernel.release.<soc> -r /System/Library/Extensions -r /System/Library/DriverExtensions -x $(kmutil inspect -V release --no-header | awk '!/AppleSerialShim/ { print " -b "$1; }')
+```
+
+Replace `<soc>` with `t8101` on M1 Macs and `t6000` on M1 Pro/Max Macs. If you’re unsure, `uname -v` and look at the end of the version string (`RELEASE_ARM64_<soc>`).
+
+Then, enter 1TR:
+
+1. Power off your Mac
+2. Press and hold the Power button until the boot menu appears
+3. Select “Options”, then (if necessary) select your macOS volume and enter your administrative password.
+
+Select Utilities>Startup security and switch the macOS installation to reduced security. Exit Startup security.
+
+Select Utilities>Terminal and install your custom kernel:
+
+```
+kmutil configure-boot -c /Volume/<volume>/Library/KernelCollections/kc.noshim.macho -C -v /Volume/<volume>
+```
+
+Replace `<volume>` with the name of your boot volume.
+
+You can now reboot: macOS should start as normal, and the serial device `/dev/cu.debug-console` should be available.
+
+To revert back to the default kernel, enter 1TR again, access Utilities>Startup security and switch to full or reduced security.
+
 ## Building
 
 Install the XCode commandline tools and type `make`.
 
 ## Usage
 
-Connect the two devices via their DFU ports. That's the furthest left port on M1 MacBooks, the closest left port on the T2, and the only port on the iPad.  See Apple's DFU recovery support articles to identify these ports on other models.
+Connect the two devices via their DFU ports. That's:
+ - the rear port on MacBook Air and 13" MacBook Pro (Apple M Series)
+ - the port next to the MagSafe connector on the 14" and 16" MacBook Pro
+ - the port nearest to the power plug on Mac Mini (Apple M Series)
+ - the closest (to the user) USB port on T2 based MacBooks
+ - the only port on the iPad / iPhone
 
 You need to use a *USB 3.0 compatible* (SuperSpeed) Type C cable. USB 2.0-only cables, including most cables meant for charging, will not work, as they do not have the required pins (USB CC1/CC2 where USB-PD are transmitted). Thunderbolt cables work too.