My laptop has a broadcom chip and yes, I've followed the related posts on this site like this one but I still have a problem. Not all features of the card work with a given configuration.
By "configuration" I mean one of the following. In the "additional drivers", there are two choices, one "bcmwl-kernel-source" and the other "Do not use device".
With the first one I can connect to routers without a problem but "laptop hotspot" does not work (of course I don't mean 'at the same time'). With the second one, I can use my laptop as a hotspot (at home), but when I'm at work or elsewhere, nm-applet does not show the available networks. (In this situation I can turn the card off and on manually then choose "connect to hidden network".)
And no, it's not blacklisted; and "bcmwl-kernel-source" is not installed. Below is the output of some relevant commands (with the second configuration):
08:00.0 Ethernet controller : Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 03) Subsystem: Dell Device [1028:02bb] Kernel driver in use: r8169
0e:00.0 Network controller : Broadcom Corporation BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01) Subsystem: Dell Wireless 1397 WLAN Mini-Card [1028:000c] Kernel driver in use: b43-pci-bridge
mon.wlan0 IEEE 802.11bg Mode:Monitor Tx-Power=20 dBm
Retry long limit:7 RTS thr:off Fragment thr:off Power Management:on
wlan0 IEEE 802.11bg ESSID:"Something"
Mode:Managed Frequency:2.437 GHz Access Point:
Bit Rate=48 Mb/s Tx-Power=20 dBm
Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off Link Quality=65/70 Signal level=-45 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:504 Invalid misc:4176 Missed beacon:0
lsmod | grep -e wl -e b43
b43 387322 0
bcma 46699 1 b43
mac80211 597268 1 b43
cfg80211 480503 2 b43,mac80211
ssb 62057 1 b43