[mythtv-users] /dev/dvb disappeared

[Leighton Brough]

David Whyte wrote:
> On 7/20/07, Jarrod Harch <jarrod.harch at gmail.com> wrote:
>   
>> I have it working again now.
>>
>> I think the problem was related to changing a PCI 802.11 card recently,
>> for some reason when I moved the DVB card into a different slot it
>> started working again.
>>
>>     
>
> I am glad you have it working again but I think you may have been luck
> this time.  I too had my DVB cards disappear on me intermittently and
> it turned out that I had to run some script at startup to get them
> working.
>
> I am not near my mythbox right now and I can't find the thread on this
>
>
> list but when I do, I will let you know.
I agree it was quite probably luck this time. I've also got a very 
similar symptom with the Twinhan DVB-T cards. It seems the kernel 
modules for this are not the best, with some unfortunate regressions in 
the later kernels which prevent me from upgrading (in particular an 
incorrect usage count which make it impossible to unload the module, 
despite claims of a fix). There seems to be some bickering on the DVB 
mailing list about these issues, but not much progress unfortunately.

I too had to write a script to keep rmmod-ing and modprobe-ing until the 
frontend devices come up correctly. Without this I find 1 or 2 of the 
cards in my system (total of 3) don't always initialise correctly. This 
is especially noticeable when re-loading the relevant kernel modules 
after a suspend-to-RAM (they don't cope with suspend-to-RAM correctly 
and have to be unloaded first or they crash the kernel). It also happens 
after a cold boot, maybe 1 time in 10 or so. Changing PCI slots seems to 
make some difference, but nothing I tried made this completely reliable. 
Before I realised what was going on this resulted in most frustrating, 
intermittent recording failures.

Here's my script, which I run at boot and on resume from suspend. It's a 
pretty nasty hack with sleeps and all, but it works:

echo "restart_dvb: starting DVB modules"
modprobe dvb_bt8xx
until [ -e /dev/dvb/adapter0/frontend0 ]  && [ -e 
/dev/dvb/adapter1/frontend0 ]  && [ -e /dev/dvb/adapter2/frontend0 ]
do
  sleep 1
  echo "restart_dvb: some devices failed to start"
  echo "restart_dvb: stopping..."
  rmmod dvb_bt8xx dst_ca dst bt878 bttv 2> /dev/null
  sleep 2
  echo "restart_dvb: restarting..."
  modprobe dvb_bt8xx
  sleep 2
done

I'd be delighted to hear if someone has a more elegant solution to this 
problem.

Cheers,
Leighton