Using the Fedora Linux I can't boot with Linux from 4.0.5 and up. 4.0.4 still works.
Here is a link to the fedora bug: https://bugzilla.redhat.com/show_bug.cgi?id=1236423
and to the linux bug here: https://bugzilla.kernel.org/show_bug.cgi?id=101131
Any more info I should add?
Please include the relevant information here directly.
Price question: Can you bisect?
If 4.0.5 is bad and 4.0.4 still works that should be pretty much straight forward.
Do you know any guide on how to bisect while using Fedora?
There are tons of git bisect howtos. You will need to checkout the stable kernel git tree, build and install it. Here are the basics:
# 1. clone the git tree
git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
# 2. copy the config from your currently running kernel
cp /boot/config-4.0.4-<whatever> .config
# 3. start the bisect
git bisect start
git bisect good v4.0.4
git bisect bad v4.0.5
# 4. build and install the kernel
# 5. reboot and test of the kernel is working
# 6a. if so mark the commit as good
git bisect good
# 6b. else mark it as bad
git bisect bad
# 7. repeat steps 4-6 until git has identified the problematic commit
I believe that the patch proposed in 91041 [1,2] will resolve this.
This bug seems to be caused by an early attempt to access the afmt property of the encoder before it has been initialised. The audio detection rework in  looks like it should avoid this corner case.
Andreas, can you try the patch linked as ?
I applied the patch you emailed me, should I try this one as well?
Yes, I suggest you try it just to confirm that the issue doesn't reappear with the new audio detect code in place.
The linked patch works as well. Should I change the status of this bug?
*** This bug has been marked as a duplicate of bug 91041 ***