On Tue, 17 Feb 2009, Steven Toth wrote: > Trent Piepho wrote: > > On Mon, 16 Feb 2009, Steven Toth wrote: > >>> Hartmut, Oliver and Trent: Thanks for helping with this issue. I've just > >>> reverted the changeset. We still need a fix at dm1105, au0828-dvb and maybe > >>> other drivers that call the filtering routines inside IRQ's. > >> Fix the demux, add a worker thread and allow drivers to call it directly. > >> > >> I'm not a big fan of videobuf_dvb or having each driver do it's own thing as an > >> alternative. > >> > >> Fixing the demux... Would this require and extra buffer copy? probably, but it's > >> a trade-off between the amount of spent during code management on a driver by > >> driver basis vs wrestling with videobuf_dvb and all of problems highlighted on > >> the ML over the last 2 years. > > > > Have the driver copy the data into the demuxer from the interrupt handler > > with irqs disabled? That's still too much. > > > > The right way to do it is to have a queue of DMA buffers. In the interrupt > > handler the driver takes the completed DMA buffer off the "to DMA" queue > > and puts it in the "to process" queue. The driver should not copy and > > cetainly not demux the data from the interrupt handler. > > I know what the right way is Trent (see cx23885) although thank you for > reminding me. videobuf_dvb hasn't convinced people like me to bury myself in its > mess or complexity during retro fits cases. Retro fitting videobuf_dvb into cx18 > (at the time) was way too much effort. > > Retro fitting it into existing drivers can be painful and I haven't seen any > volunteers stand up over the last 24 months to get this done. > > My suggestion? For the most part we're talking about very low data rates for > DVB, coupled with fast memory buses for memcpy's. If the group doesn't want > calls to the sw_filter methods then implement a half-way-house replacement for > those drivers - as I mentioned above - with the memcpy. Either this approach, or The problem is holding a spin lock with irqs disabled for a long amount of time. What exactly is your plan that will remove this, yet allow drivers to process their buffers from an irq handler? > A general question to the group: Who wants to volunteer to retro fit > videobuf_dvb into the current drivers so we can avoid calls to sw_filter_...n() > directly? I don't see why videobuf_dvb is needed. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
