> >> If I have a USB camera with good Linux support, can I connect it > >> to omap3evm(or any omap2) and make it functional? I'm told some folk have used ISO transfer support, but when I last did much work with the musb code, none of it was tested. > > I don't see why not. Do you expect a problem with using it? You could > > use MUSB in host or OTG mode and connect the camera to the MUSB port. > > Not quite, MUSB doesn't support the 'high bandwidth' flag, which most > usb webcams seem to use (even the puny 12mbit ones). Tested on the > MUSB port of my beagle and bf548. Since "high bandwidth" is a mode restricted to 480 mbps hardware, I think generic ISO transfer problems are more likely the issue than anything related to isochronous video streams topping 8 MByte/second... no 12mbit camera can possibly care about high bandwidth. The integrated MUSB controllers (2430, OMAP3[45]xx) have hardware support for "high bandwidth". Technically, "high bandwidth" is when you have a 480 Mbit/sec connection and it's issuing more than one isochronous or interrupt packet per microframe (8 microframes/msec). Those packet top out at 1 KByte each, ergo 8 MByte/second is the most you can get without high bandwidth support. Endpoints can issue at most three such packets per microframe ... so, max 24 MByte/sec is the most you can get *with* high bandwidth support. (The USB 2.0 spec is self contradictory about whether you can have two streams at that rate going concurrently. One is clearly OK; two would exceed the bandwidth reserved for periodic transfers, by around 3%.) So ... first, someone should get ISO to work well. Start with full speed webcams, which can do one 1023 byte packet per millisecond. I think you'll need to make sure double buffering works right, and tweak the default FIFO allocations a bit. Then go to high speed webcams, and make sure that same code can work eight times faster (one 1024 byte packet every microframe, you get an extra byte). Then it's time to work on the high bandwidth stuff. - Dave -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
