, your chip doesn't seem to be supported :
PCI-ID State Chip Driver
14e4:4315 not supported BCM4312 802.11b/g - low power b43
* The 802.11a part of the 4309 and 4312 is not supported.
The driver b43 is included in the kernel ; it should be :
Look the messages from dmesg to know what the kernel does with it.
The link above give detailed infos on how to use/configure the driver, but if nothing has changed you seem to be out of luck with this chipset.