Unable to access hosts beside local host in Ansible - ansible

Question

I'm self-learning ansible and having the files structure below with my customized ansible.cfg and inventory file:
---ansible (Folder) <---Working level
---ansible.cfg (Customized cfg)
---dev (Inventory File)
---playbooks (Folder) <--Issue level
---hostname.yml
ansible.cfg
[defaults]
inventory=./dev
dev
[loadbalancer]
lb01
[webserver]
app01
app02
[database]
db01
[control]
control ansible_connection=localansible
hostname.yml
---
- hosts: all
tasks:
- name: get server hostname
command: hostname
My question is when I run ansible-playbook playbooks/hostname.yml at ansible (Folder) level, everything works fine
PLAY [all] *********************************************************************
TASK [setup] *******************************************************************
ok: [control]
ok: [app01]
ok: [db01]
ok: [lb01]
ok: [app02]
TASK [get server hostname] *****************************************************
changed: [db01]
changed: [app01]
changed: [app02]
changed: [lb01]
changed: [control]
PLAY RECAP *********************************************************************
app01 : ok=2 changed=1 unreachable=0 failed=0
app02 : ok=2 changed=1 unreachable=0 failed=0
control : ok=2 changed=1 unreachable=0 failed=0
db01 : ok=2 changed=1 unreachable=0 failed=0
lb01 : ok=2 changed=1 unreachable=0 failed=0
Howevery when I go into the playbooks folder and run ansible-playbook hostname.yml it give me warning saying
[WARNING]: provided hosts list is empty, only localhost is available
PLAY RECAP *********************************************************************
Is there anything that prevents playbook from accessing the inventory file?

Answer 1

Ansible does not traverse parent directories in search for the configuration file ansible.cfg. If you want to use a custom configuration file, you need to place it in the current directory and run Ansible executables from there or define an environment variable ANSIBLE_CONFIG pointing to the file.
In your case: changing the directory to ansible and executing is the proper way:
ansible-playbook playbooks/hostname.yml
I don't know where from you got the idea Ansible would check for the configuration file in the parent directory - the documentation is unambiguous:
Changes can be made and used in a configuration file which will be processed in the following order:
ANSIBLE_CONFIG (an environment variable)
ansible.cfg (in the current directory)
.ansible.cfg (in the home directory)
/etc/ansible/ansible.cfg