[mythtv-users] controlling order of tuner card detection?

Rod Smith mythtv at rodsbooks.com
Sun Mar 4 19:51:13 UTC 2007

On Sunday 04 March 2007 14:19, Michael Thome wrote:
> Sometimes, my tuner cards are detected and thus assigned to /dev/videoX
> numbers in different orders - this wouldn't be an issue except that they
> have very different connections and features.  Right now, I've got a
> pvr-150 with both cable and video-in and a hd5500 with qam and backup
> cable in - if they get detected in the wrong order, /dev/video doesn't
> have an mpeg encoder, doesn't have an attached cable box to video0, and
> gets darn nasty reception.  I've been planning to replace the 150 with a
> 500, but I'm nervous that it'll make things even worse...
> Is there any way to force detection to proceed in bus-order, presumably
> not changing unless I swap cards?

I've not dealt with this issue specifically, but I have dealt with similar 
problems, and I can suggest two possible approaches to fixing the problem:

1) Build the drivers for one card into the kernel and build the drivers for
   the other card as modules. The drivers built into the kernel should then
   load and detect the device first, ensuring that the relevant device gets
   the lower number (/dev/video0). This trick has worked for me in the past
   with SCSI devices, but I've not tried it with video cards.

2) Muck with your udev configuration (assuming you're using udev). The
   /etc/udev/rules.d directory contains udev rule files. You should be
   able to create a new one that creates device files separate from the
   /dev/video* files. Presumably you'd create unique files for each
   device, such as /dev/video-pvr150 and /dev/video-hd5500. Unfortunately,
   it'll take some study to figure out how to set this up. If you happen
   to subscribe to the US Linux Magazine, I wrote a piece on udev for the
   November 2006 issue that should point you in the right direction
   (although it doesn't cover video devices explicitly). If not, try a
   Web search; that should turn up lot of information. The tricky part
   will be using udevinfo or some other tool to locate unique information
   about each device/driver to use to create the device-specific device
   files. Once you've got this working, you'll be able to refer to the
   devices in mythtv-setup via their unique names rather than their
   generic /dev/video? names.

Rod Smith

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