When developing a module that might need to modify files in a specific directory like /mnt/vendor/persist/modem/cpsha, it's important to understand the file system layout and the permissions required for such operations. In many cases, directories outside of /system are protected and require special considerations for modification. Here are some steps and considerations for replacing files in directories other than /system:

  1. Identify the Directory's Purpose: Understand why the directory /mnt/vendor/persist/modem/cpsha exists and what files it contains. This will help determine if it's safe and appropriate to modify these files.
  2. Check Filesystem Type: Determine the type of filesystem that the directory is using. Some filesystems might have restrictions on file modifications that are not present in others.
  3. Permissions and Ownership: Verify the permissions and ownership of the directory and files. You may need root or specific user permissions to modify files in this directory.
  4. Backup Files: Before making any changes, ensure that you have a backup of the original files. This allows you to restore them if something goes wrong.
  5. Testing Environment: If possible, test your module in a controlled environment that mimics the production environment. This can help catch any issues before deploying to a live system.
  6. Consult Documentation: Look for any documentation that might explain how to safely modify files in this directory. Sometimes manufacturers provide guidelines for developers.
  7. Use Filesystemless Replacement: If you are used to replacing files systemlessly in /system, consider if the same approach can be applied to /mnt/vendor/persist/modem/cpsha. This might involve using a recovery image or a custom script that can modify files in other directories.
  8. Seek Support: If you're unsure, seek support from the community or the device manufacturer. They may provide insights or tools that can help with file modifications in these directories.

Remember, modifying system files, especially in directories managed by the vendor, can lead to instability or bricking the device if not done correctly. Always proceed with caution and ensure you have a plan to revert changes if necessary.