Updated README

README.md

@@ -1,6 +1,6 @@
 # NVIDIA Jetson driver
 
-Driver for Allied Vision Alvium cameras with MIPI CSI-2 interface for NVIDIA Jetson with JetPack 4.4.1 (L4T 32.4.4)     
+Driver for Allied Vision Alvium cameras with MIPI CSI-2 interface for NVIDIA Jetson with JetPack 4.5.1 (L4T 32.5.1)     
 https://developer.nvidia.com/embedded/jetpack
 ![Alvium camera](https://cdn.alliedvision.com/fileadmin/content/images/cameras/Alvium/various/alvium-cameras-models.png)
 
@@ -9,35 +9,27 @@ https://developer.nvidia.com/embedded/jetpack
 The scripts in this project build and install the Allied Vision CSI-2 driver to the NVIDIA Jetson boards.
 
 Platforms: Nano, Nano 2GB, TX2, AGX Xavier, Xavier NX    
-JetPack 4.4.1 (L4T 32.4.4)  
+JetPack 4.5.1 (L4T 32.5.1)  
 The scripts require Git on the host PC.
 
 ***Before starting the installation, make sure to create a backup of your Jetson system.***
 
-## Prerequisites: Install JetPack 4.4.1 to Jetson Nano, Nano 2GB, TX2, AGX Xavier or Xavier NX
+## Prerequisites: Install JetPack 4.5.1 to Jetson Nano, Nano 2GB, TX2, AGX Xavier or Xavier NX
 
-1. Install JetPack 4.4.1 (L4T 32.4.4) as per NVIDIA's instructions https://developer.nvidia.com/embedded/jetpack   
+Install JetPack 4.5.1 (L4T 32.5.1) as per NVIDIA's instructions https://developer.nvidia.com/embedded/jetpack   
     Recommendation: Use NVIDIA SDK Manager to install JetPack and useful tools such as CUDA.   
     https://docs.nvidia.com/sdk-manager/  
 
-2. Update and upgrade the host PC and the Jetson board:   
-   `# sudo apt update`   
-   `# sudo apt upgrade`
+### Accidental overwriting of the driver
+As of JetPack 4.4, users can update L4T directly on the board with `apt-upgrade`. 
+Doing this may install newer L4T kernel and device tree files, which overwrite the driver for Allied Vision cameras. 
+If you use `apt-upgrade` nevertheless, please prevent overwriting the driver with `sudo apt-mark hold nvidia-l4t-kernel nvidia-l4t-kernel-dtbs`.
+Note that both reinstalling the driver or putting the update on hold may cause unavailable features or bugfixes from NVIDIA.
 
 ## Install Alvium CSI-2 driver to Jetson Nano, Nano 2GB, TX2, AGX Xavier or Xavier NX
 
- **Method A: Use precompiled binaries**   
-  Install the precompiled kernel including driver and installation instructions:   
-  https://www.alliedvision.com/en/products/software/embedded-software-and-drivers/
-
-  1. Extract the tarball on a host PC.
-
-  2. The tarball contains helper scripts and another tarball with the precompiled binaries named AlliedVision_NVidia_L4T_32.4.4_<git-rev>.tar.gz.   
-     Copy the tarball to the target board. On the target board, extract the tarball and run the included install script.   
-     Reboot the board. Now you can use the driver. 
-
- **Method B: Cross-compile binaries from source**    
-  These scripts require a host PC with Ubuntu (16.04 or 18.04) installed.
+ **Cross-compile binaries from source**    
+  These scripts require a host PC with Ubuntu (18.04) installed.
 
   1. Download sources and scripts from https://github.com/alliedvision/linux_nvidia_jetson to the host PC.   
      On the host PC:
@@ -59,4 +51,3 @@ The scripts require Git on the host PC.
  ## Additional information
  :open_book:
  https://github.com/alliedvision/documentation/blob/master/NVIDIA.md
-