Here is the announcement.  I tested the code on Diamond Multimedia Stealth 3D 2000 (S3 ViRGE, 2 MB EDO DRAM, PCI bus) and Stealth 3D 4000 (S3 ViRGE / GX2, 4 MB SGRAM, AGP bus) with Xubuntu 16.04.5 (X Server 1.19.6).  Standby resume does not work.  If anyone has the hardware register documentation, feel free to e-mail me as long as you do not violate your NDA.