hi Rob,

thank you for doing the test so fast - i understand Adam won't like what i will say, but your test results show that what i stated as hypothesis earlier is true and what i further elaborated as contra-arguments to Adam's statement that's fault of TBS drivers is correct too. so, considering i'm quite sure those OSS drivers Adam mentioned doesn't implement things from the API like 'get_frontend' ioctl that means they work only due to that, i.e. not due to some big magic and superiority, but because they already have lowered number of transactions due to those missing things or the same reason for which "linux-tbs-drivers_6981_11.tar.bz2" works for you. so, everything adds up now.

what we can do as next steps is one-by-one re-add the things i removed from the driver to lower the transactions until their number reach the point when TVH will cause overload and break the work. also, 'get_frontend' ioctl is my main suspect at the moment, because no OSS driver in Linux implements that, because it's quite hard - even when you have datasheets under NDA there is usually not enough information to implement it, but it's mandatory requirement by all customers doing professional-grade solutions. so, maybe, soon we will be able to say something quite concrete like TVH causes overload when there is 'get_frontend' ioctl implemented or something like that due to most likely some timing problem, because that ioctl is called by V4L on lock acquisition. anyway, as next step i will flood you with at least several drivers that re-adds different things from what i removed to test them in order to narrow it down until it's pin-pointed. in any case there is no doubt for me TVH has some implementation problem, because removing things defined in Linux DVB API made it works normal, that's not normal, no matter if Adam admits it or not. also, from driver point of view there is almost no freedom how to implement the API, but from application point of view there are for sure wrong ways to use the API.

BTW, there is no point to do the IR test, because obviously from your test results it's not that - current conclusion is quite clear - that with way how TVH access the frontends the frontend driver needs to make limited number of transactions otherwise TVH will cause overload and it seems the number of transactions that driver for 6981 is doing is close to that threshold, i.e. removing not that much transactions made the work stable even in such case. however, that's really huge performance degradation caused by TVH considering what i mentioned several times - that we have customers running 16 or even 32 x 6981 cards in the same system via PCIe back-planes with DVBlast and overload happens only with 2 tuners of one such card when the card is used with TVH. also, it means, the other Dual tuner cards that are working fine with TVH are probably working only because they have faster frontend chips that can take those transactions without overload.

best regards,
konstantin