Jon Smirl wrote: > On Thu, Apr 8, 2010 at 1:10 AM, Mauro Carvalho Chehab > <mchehab@xxxxxxxxxxxxx> wrote: >> David Härdeman wrote: >>> drivers/media/IR/ir-raw-event.c is currently written with the assumption >>> that all "raw" hardware will generate events only on state change (i.e. >>> when a pulse or space starts). >>> >>> However, some hardware (like mceusb, probably the most popular IR receiver >>> out there) only generates duration data (and that data is buffered so using >>> any kind of timing on the data is futile). >>> >>> Furthermore, using signed int's to represent pulse/space durations in ms >>> is a well-known approach to anyone with experience in writing ir decoders. >>> >>> This patch (which has been tested this time) is still a RFC on my proposed >>> interface changes. >>> >>> Changes since last version: >>> >>> o RC5x and NECx support no longer added in patch (separate patches to follow) >>> >>> o The use of a kfifo has been left given feedback from Jon, Andy, Mauro >> Ok. >> >>> o The RX decoding is now handled via a workqueue (I can break that up into a >>> separate patch later, but I think it helps the discussion to have it in for >>> now), with inspiration from Andy's code. >> I'm in doubt about that. the workqueue is called just after an event. this means >> that, just after every IRQ trigger (assuming the worse case), the workqueue will >> be called. >> >> On the previous code, it is drivers responsibility to call the function that >> de-queue. On saa7134, I've scheduled it to wake after 15 ms. So, instead of >> 32 wakeups, just one is done, and the additional delay introduced by it is not >> enough to disturb the user. > > The wakeup is variable when the default thread is used. My quad core > desktop wakes up on every pulse. My embedded system wakes up about > every 15 pulses. The embedded system called schedule_work() fifteen > times from the IRQ, but the kernel collapsed them into a single > wakeup. I'd stick with the default thread and let the kernel get > around to processing IR whenever it has some time. Makes sense. > A workqueue has to be used at some point in the system. The input > subsystem calls that send messages to user space can't be called from > interrupt context. I believe in handing off to the workqueue as soon > as possible for IR signals. I'm ok on using a workqueue for it. > > Keep this code in the core to simplify writing the drivers. My GPIO > timer driver example is very simple. > > If you're worried about performance, none of this code matters. What > is more important is localizing memory accesses to avoid processor > cache misses. A cache miss can equal 1000 divides. Agreed. -- Cheers, Mauro -- 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
