Not able to read the attribute with string type value

[yufengwangca]

Problem

I found the default generated attribute get API does not work for the attrbute with type of string, such as:

namespace Description {
EmberAfStatus Get(chip::EndpointId endpoint, chip::MutableCharSpan value); // char_string
EmberAfStatus Set(chip::EndpointId endpoint, chip::CharSpan value);

The Set API works well.

Proposed Solution

<suggested fix, suggested enhancement>

[bzbarsky-apple]

The MutableCharSpan passed in needs to point to a buffer to copy the string into. And the read will fail if the buffer is not big enough.