Looking at my Solaris Express 11 the driver installed is 256.53. Looking at the release notes here:
it shows about 2/3's the way down "NVS 3100M 0x0A6C". This shows the card is supported by this driver.
What you may have to do is add support for your chipset in /etc/driver_aliases.
The way one goes to check this is, and I'll use my Nvidia FX5800 card as an example.
Enter the command:
Search the output for the listing ]s with Nvidia in it, mine shows:
pci bus 0x000f cardnum 0x00 function 0x00: vendor 0x10de device 0x05fd
nVidia Corporation GT200GL [Quadro FX 5800]
Now looking on the supportedchips.html earlier shows my card as:
"Quadro FX 5800 0x05FD"
Looking in the file /etc/driver_aliases I found:
What your looking at is the 5fd is common to all three examples. Sometimes the driver_aliases doesn't get all chipsets listed and you have to manually add an entry. The correct chipset to add is the one displayed from the output of "scanpci".
So the first thing to do is run scanpci to see what chipset is listed.