Ubuntu – Building driver for Ralink RT5370 USB WiFi WLAN Dongle

I have a Trim-Slice Value using Ubuntu 11.04. It comes with a Ralink RT5370 802.11n WiFi dongle.

When I plug the dongle in, it does not 'just work'; ifconfig and iwconfig do not show the device, though lsusb does show the device listed:

phrogz@trimslice:~$ lsusb | grep Ralink
Bus 001 Device 004: ID 148f:5370 Ralink Technology, Corp. 

I downloaded the link for RT5370 from Ralink's Linux Drivers site, resulting in a file named 2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO.tar.bz2. After extracting it, the only README in the file mentions the "RT2870 Wireless Lan Linux Driver"; however, the Makefile at the root of the directory does have these lines:

ifeq ($(CHIPSET),)
CHIPSET = 5370
endif

I edited os/linux/config.mk to have these settings:

# Support Wpa_Supplicant
HAS_WPA_SUPPLICANT=y

# Support Native WpaSupplicant for Network Maganger
HAS_NATIVE_WPA_SUPPLICANT_SUPPORT=y

When I return to the root of the extracted directory and run make, however, it fails:

phrogz@trimslice:~/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO$ sudo make
[sudo] password for phrogz: 
make -C tools
make[1]: Entering directory `/home/phrogz/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO/tools'
gcc -g bin2h.c -o bin2h
make[1]: Leaving directory `/home/phrogz/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO/tools'
/home/phrogz/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO/tools/bin2h
cp -f os/linux/Makefile.6 /home/phrogz/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO/os/linux/Makefile
make -C /lib/modules/2.6.38.3-trimslice-1.03/build SUBDIRS=/home/phrogz/2011_0225_RT5370_RT5372_Linux_STA_V2.5.0.1_DPO/os/linux modules
make: *** /lib/modules/2.6.38.3-trimslice-1.03/build: No such file or directory.  Stop.
make: *** [LINUX] Error 2

How can I build the driver for this device?