[mythtv-users] Udev

[Stephen Worthington]

On Tue, 27 Nov 2018 12:33:45 +0000, you wrote:

>On 27/11/2018 11:35, Daryl McDonald wrote:
>> Due to recent hardware problems I've ordered a new motherboard, and 
>> because it has more PCI slots I've ordered more tuners. Since I now 
>> have only one source for recording Udev rules wont be necessary 
>> because it wont matter which tuner is asked to record, or will it?
>>
>> I may just create them anyway, but it wont be without challenge, 
>> because one card is the same model as an existing card.    Daryl
>>
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>
>I have never got a dual card working reliably. They tend to fail about 
>once a week on boot. (multiple single tuner cards have been completely 
>reliable). A reboot always fixes the problem and the cards are then 100% 
>reliable until power on.
>
>I have been using the "Example for twin tuner cards with no difference 
>in udevadm info output" from the wiki
>
>https://www.mythtv.org/wiki/Device_Filenames_and_udev
>
>but having re-read it (maybe its been updated) I think my problem is the 
>race condition as described in "More complicated setup with multi-tuner 
>cards having no difference in udevadm info output coexisting with other 
>cards based on the same A/V decoder" . The issue being that it is 
>possible to receive adapterX with frontend from adapterY. The symptom 
>being the tuner gets the signal ok but with only a partial lock because 
>it cant find the channel its looking for in the stream.
>
>So I am currently testing a dual PCI and a dual USB card together 
>without using udev. Its been a week with no issues but I know this is 
>perhaps only luck.
>
>Trying to get my head round the solution proposed in "More complicated 
>setup with multi-tuner cards having no difference in udevadm info output 
>coexisting with other cards based on the same A/V decoder" but having 
>difficulty understanding it.
>
>The bottom line is - if you get partial tuner locks on a dual card with 
>errors like this /dev/dvb/adapter2/frontend0): Wrong PMT; pmt->pn(6033) 
>desired(6031) the solution possibly lies at the end of the wiki.

As long as you do not move the tuner cards to different slots, the
kernel will always enumerate the cards in the same order.  When there
are multiple tuners on one card, unless the drivers have a horrible
bug, the tuners will be enumerated in the same order on the card at
each boot.

Your problem with multiple tuners on one card or USB device sounds
like a driver bug.  I have one dual tuner USB device that is like that
- a Kworld DVB-T 399UR.  It supposedly works in Linux, but the Linux
driver has a bug in that it treats the two devices as completely
separate tuners, when they in fact have a bit of hardware that is
shared between them.  So when one tuner sets that bit of hardware, it
overwrites the settings written by the other tuner, and that causes
chaos.  If I just use one of the tuners, it works fine.  If I use both
tuners at once, neither tuner is guaranteed to work.  So I have had to
put that tuner on my Windows box, where it works well.

I two have other multi-tuner cards (TBS-6909 8 tuner DVB-S2 and
TBS-6209 8 tuner DVB-T2 PCIe), but their drivers work well and there
is no interference between the tuners.