Comment 10 for bug 762987

We've made progress.

I've tested the rt2870.bin file from linux-firmware 1.53 which works :-). You still have to blacklist rt2870sta because otherwise nothing ralink-related is loaded. Syslog:

Jun 2 09:41:26 sixpack NetworkManager[1024]: <info> (wlan0): new 802.11 WiFi device (driver: 'rt2800usb' ifindex: 3)
Jun 2 09:45:45 sixpack kernel: [ 70.043618] usbcore: registered new interface driver rt2800usb
Jun 2 09:47:12 sixpack kernel: [ 14.136337] Registered led device: rt2800usb-phy0::radio
Jun 2 09:47:12 sixpack kernel: [ 14.136360] Registered led device: rt2800usb-phy0::assoc
Jun 2 09:47:12 sixpack kernel: [ 14.136371] Registered led device: rt2800usb-phy0::quality
Jun 2 09:47:12 sixpack kernel: [ 14.137068] usbcore: registered new interface driver rt2800usb

lsmod:

rt2800usb 18235 0
rt2800lib 45181 1 rt2800usb
crc_ccitt 12667 1 rt2800lib
rt2x00usb 20330 1 rt2800usb
rt2x00lib 49235 3 rt2800usb,rt2800lib,rt2x00usb
mac80211 294370 3 rt2800lib,rt2x00usb,rt2x00lib
cfg80211 178528 2 rt2x00lib,mac80211

Additionally, I tested the rt2870-firmware from the ralink website as described in Bug 782752. This also works, but not as good as the one from linux-firmware. NetworkManager is reacting slow on connecting/disconnecting and the syslog shows the following:

Jun 2 09:33:13 sixpack kernel: [ 288.072780] phy0 -> rt2x00usb_vendor_request: Error - Vendor Request 0x06 failed for offset 0x1328 with error -71.

But the one from linux-firmware is working great, I will test it for some days to check its stability, speed etc.
Thank you for your help + your explanations, I learned a bit more about linux' wifi architecture. :thumdsup