Changes in 8192cu stopped ability to scan wifi-networks

[mr-berndt]

Hi,

trying to upgrade my system to run on the new raspberry 2, I ran into trouble with my wireless-dongle EDIMAX EW-7811UN (7392:7811). It uses the 8192cu module and after compiling the new 3.18.7 kernel, the module loads but tells me that my wifi-dongle doesn't support scanning of the networks, which it did before and without I cannot work.

Out of curiousity I installed raspian (have a small self-built busybox system otherwise) and found the 8192cu module to enable scanning there. Modinfo told me, that the module used in that particular 3.18.7 kernel was from Realtek itself, modinfo on my 3.18.7 kernel from github doesn't.

Following issue #755 #755 I tried including the realtek-source right in my (cross-compiled) kernel-source-tree but ended up having the mentioned proc-issue upon compilation. Looking for the CONFIG_PROC_DEBUG portion in my kernel .config, I found this option to be non-existant (anymore?), so this is where I give up and now ask for help here..

Which driver exactly IS included in 3.18 right now and why has it changed from 3.16 where it was working like a charm? What can I do to get a 8192cu module again, that supports scanning of it's surrounding?

Help would of course be very appreciated!
Best regards
Nico

[popcornmix]

The upstream 8192cu is widely regarded as unusable (see #755)
So, we include the out-of-tree Realtek driver.
Raspbian uses the rpi-3.18.y tree and is built with config from:

make ARCH=arm bcm2709_defconfig

which will be using the out-of-tree Realtek driver.

I'd suggest you build the default tree with default config.
I'm afraid I can't offer support for the known buggy upstream 8192cu driver.

[mr-berndt]

I'm afraid, I don't understand. The driver included in the regular 3.18 kernel-source from github breaks scanning for me, so I would consider this the broken driver, or not? I failed compilation when I tried to include the Realtek-driver.

So this leaves me with a not fully-functioning driver in the regular kernel-sources from github and a non-compiling driver from Realtek.

Which of these drivers is the "upstream"-driver and which can you support? I'm confused here, sorry..

[mr-berndt]

OK, maybe I should have read your post more careful, sorry. So I understand that the driver included in 3.18 IS the Realtek-driver. Now I don't understand why scanning doesn't work, when it does work using stock raspbian with 3.18, since in raspbian modinfo tells me, that the driver is the one from Realtek and should be no different from the driver I get compiling 3.18 myself.

[popcornmix]

Are you building with our bcm2709_defconfig? I'd start with that and then make changes.

[mr-berndt]

I have a very small 3.16 self-configured kernel with just 5 or 6 modules. Oldconfig gave me trouble and so I went from bcm2709_defconfig an threw out a lot of drivers which I knew were external hardware, so actually I should be good. I will try how the full bcm2709_defconfig behaves and report back..

[mr-berndt]

OK, bcm2709_defconfig really did the trick, I can scan again!

A new problem came up, though, I am getting a "unable to handle kernel paging request at address ffffffff" but I will have to fix that myself, it is not happening with the same kernel on raspbian, so there must be some issue with my system.

Thanks for the help!