The chirp_common.DTCS_CODES list can be added to and subtracted from by the driver author in order to match the selections that are available in the radio. For example the the driver for the UV-5R adds the DTCS 645 code to the chirp_common.DTCS_CODES list to match the list of DCS codes that the UV-5R (and UV-5R like radios) support.
UV5R_DTCS = sorted(chirp_common.DTCS_CODES + [645])
The Leixen driver adds DTCS 017, 050 and 645 to the chirp_common.DTCS_CODES list to match what the radio supports.
DTCS_CODES = [17, 50, 645] + chirp_common.DTCS_CODES
Adding any additional codes would not be worthwhile because the radio does not support them.
Some radios do allow programming a 1024 (512 + and 512 -) DTCS codes. CHIRP supports all 1024 codes for those radios.
One thing that I learned recently is that many of the DTCS codes are not unique. The digital code generated is actually the same as one or more other codes. For example, the following codes are basically interchangeable: +224, +313, +506, +574, -073, -640. I was amazed when I took 2 radios and programmed one with a channel using DTCS code set to 506N and the other with the same frequency and the DTCS code set to 073R and was able to communicate between the 2 radios.
So accessing a repeater that is using the non-standard +224, +313, +574 or -640 DTCS code can be accessed by programming either the standard +506 or the -073 DTCS code.
Unfortunately there are no standard DTCS code "matches" for the non-standard +024 and +124 DTCS codes.
See this "DPL / DCS Information":http://www.onfreq.com/syntorx/dcs.html page for more information.
Jim KC9HI