[mythtv-users] Cards keep changing /dev/videoX devices...

[R. G. Newbury]

Steve Smith wrote:
> Alan,
> 
> Great! Nice and simple...
> 
> I do like the idea of a udev "freeze/dump current config" type feature,
> that'd be really useful for the generic case...
> 
> Cheers
> 
> Steve
> 
> On 14/06/07, Alan Calvert <cal at graggrag.com> wrote:
>>
>> Steve Smith wrote:
>> > I have two cards in my system; a PVR-150 and a WinFast DTV-1000T.
>> >
>> > The devices work "OK", but every reboot get assigned /dev/video0 and
>> > /dev/video1 in a random order so the myth config keeps getting
>> > messed up.
>> >
>> > Is there anyway to stabilise them?
>>
>> Messing with udev rules to control this is unnecessary, and overly
>> complicated. Most of the driver modules take a parameter to specify
>> what device it should use when modprobed. With ivtv, it's
>> 'ivtv_first_minor',
>> and with cx8800 (the DTV-1000) it's  video_nr and radio_nr. Try
>> 'modinfo ivtv' and 'modinfo cx8800' (as root) for the full list of
>> options .
>>
>> I have the same mix of cards in my system, two DTV-1000's actually,
>> and in a file /etc/modprobe.d/mythtv I have ...
>>     options cx8800 video_nr=0,1 radio_nr=0,1 vbi_nr=0,1
>>     options ivtv pal=BG ivtv_first_minor=2
>> So the two DTV1000s are always /dev/video0, /dev/video1, and the
>> PVR-150 always comes up as /dev/video2 (and friends).
>>
>> Simple as that. Cheers!

You should also understand that the cx88 driver is built into the 
kernel, and will be called/installed before the ivtv driver is 
called/installed. And the 'wrong' cx88 driver might be the one the 
kernel installs, as it hasn't yet looked at modprobe.conf.

This causes problems where an HD3000 is being used for digital. You 
wouldn't want the cx8800 driver (and /dev/video0 being stolen). You 
would want the cx88_dvb driver being loaded instead. The answer is to 
blacklist the driver you do NOT want (or ALL of them), and remove 
drivers, if necessary, from modprobe.conf, and load your drivers in 
order, in rc.local.

So, for my setup, I blacklisted cx8800 and cx88_dvb, and then loaded 
cx88_dvb by a line in rc.local. The PVR500 then gets /dev/video1 and 
video2, through the ivtv driver, and there will be nothing in the way, 
and that is the first driver call to latch onto that spot.

In your case, the cx8800 driver is likely being loaded by the kernel as 
soon as the hardware is recognized. But your modprobe.conf is likely set 
up on the assumption that the ivtv driver will be called first (you 
listed it first, and computers *ALWAYS* do exactly what we want, and in 
the order we want...right? Right?).

You might want to try commenting out everything in modprobe.conf and see 
what ends loaded. Then try 'modprobe -r cx8800' in rc.local and see if 
anything at all is loaded. Then try the ivtv lines in modprobe.conf. And 
finally, try a 'modprobe cx8800' in rc.local.

I would bet (a small wager!) that the last is a stable result.

Been there, cursed at it too.....

              R. Geoffrey Newbury			


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