If you are upgrading your HP/Compaq 6715b to Debian Jessie, and suddenly Wifi stops working because the PCI device is gone, install the "rfkill" package:

# lspci | tail -2
02:04.1 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller (rev 02)
10:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5787M Gigabit Ethernet PCI Express (rev 02)

# rfkill list 1
1: hp-wifi: Wireless LAN
    Soft blocked: yes
    Hard blocked: no

# rfkill unblock wifi

# rfkill list 1
1: hp-wifi: Wireless LAN
    Soft blocked: no
    Hard blocked: no

# lspci | tail -2
10:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5787M Gigabit Ethernet PCI Express (rev 02)
30:00.0 Network controller: Broadcom Corporation BCM4311 802.11a/b/g (rev 02)

Reports on the internet say that the same could be done by going into the BIOS and selecting "Reset to default" - this makes the Wifi LED active until about udev is started on the next boot.

To be done: figure out how to automate this.