Add a command to read flash partitions including nvs

[pguyot]

esp32 nvs partition has a specific format and behavior and we could extract this from existing devices. Since we offer an API with a namespace and a key, we could have the option to dump the content of a given key for a given namespace, or list all keys and namespaces.

[UncleGrumpy]

I have a plan for this under development. I need to add read support to the esp_nvs tool/APIs in UncleGrumpy/eee_tools and I will incorporate that into a plugin task, as well as another task to flash NVS with provisioned key-values from a csv file.

[UncleGrumpy]

... we could have the option to dump the content of a given key for a given namespace.

We could certainly have the option of listing the contents of arbitrary keys, but what did you have in mind for dumping a single key? Did you want just the raw value written to a binary file? I can see that working, especially since ESP-IDF nvs_partition_gen.py and my Erlang esp_nvs tool have the option of including the raw binary contents of a file in the csv table file for a key's value. Otherwise it is hard to dump the complete raw NVS entry for a single key in a way that can be reused. There is a lot of other information encoded in the table and entry headers that will be corrupted inserting this raw entry data back into an NVS partition.

[pguyot]

The idea indeed is to dump the value in a single file, then with a shell we could do

{ok, B} = file:read_file("value.bin"),
binary_to_term(B).

or module:deserialize(B), etc.

[UncleGrumpy]

Great. That helps with design descriptions. I think I will create an nvs task, this will take a command option, either create (from csv —-input Path), dump (to file), or list (display output). The dump command will dump the entire NVS partition by default, or if a —-key Namespace Key ({key, {Namespace, Key}} in the config) is given dump just the value of the key, to a supplied —-output Path.

[UncleGrumpy]

I will have the esp32_flash task depend on the nvs task, so if any of these options are in the config they will be executed before flashing the application to the device… if the nvs create task-command is given the new NVS partition will also be flashed.