the locations of the files is

<TFTPBOOT>/grandstream/
  rings/	- custom rings
  configs/	- configs for the phones
  firmwares/	- firmwares directory
  	1.0.6.7/
	1.0.7.11/
	


HOWTO

I have added new option for atftpd "--grandstream <filename>",
where the filemane has following content
--- cut ---
<mac prefix>	<firmware>
<mac prefix>	<firmware>
<mac prefix>	<firmware>
000b8203a       1.0.7.11
000b82          1.0.6.7
--- cut ---
The first prefix which match is applied, so the 000b82/default 
firmware must be the last one.


FIRMWARES
Firmwares are served according the previuos section

CONFIGS
Configs are served from <TFTPBOOT>/grandstream/configs/cfg<mac>

RING TONES
Ring tones are served from <TFTPBOOT>/grandstream/rings/ring?.bin_<mac>

It's good to set verbose=7 for debuging informatios ;)