On 23 March 2010 19:32, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 23 Mar 2010, Pedro Ribeiro wrote: > >> This is messing with my mind. I've been desperately trying to find a >> pattern here. Now it appears the interference only happens if I unplug >> and replug the DVB-T adapter. >> >> Anyway, I have created an attachment to the original bug report with >> usbmon logs from the audio card. >> One of them shows normal operation, the other shows the interference >> I'm talking about. >> A third one (called interference2) is probably more useful - it shows >> how the interference starts when I disconnect and reconnect the DVB >> adapter. > > I didn't see anything especially unusual in the usbmon traces, except > that a little under half of the packets have length 0. But that was > true in the normal trace as well. > > (One little bug in the sound card did show up, but it isn't related to > your problem. The string-0 descriptor is invalid -- it contains an > extra byte.) > > Unfortunately the data sets are too large to examine very closely. > >> To reply to Alan's question, sometimes when I unload and reload the >> module the interference starts, sometimes it doesn't. Like I said, >> seems completely random! > > That's different from what you said originally -- you said that the > interference would start only when you unplugged and replugged the > audio card (and now when you unplug and replug the DVB-T adapter). > But unloading and reloading the driver is a software event, not a > hardware event, so the fact that it also can cause the interference to > start may be significant. Although I don't know just what it means... > > Is it still true that if you don't unplug either card or unload the > drivers then the interference never starts? > > Were you able to collect the dmesg log with CONFIG_USB_DEBUG enabled? > > Alan Stern > > I have some really interesting developments. I think I narrowed it down. So I ALWAYS get the interference when I: - load the snd-usb-caiaq module - load the dvb_usb_dib0700 module In this order. If its in the opposite order, nothing happens. So now I'm 100% sure this happens when loading and unloading modules, which like you said means its something in software, much to my relief (means its solvable). But now I have no idea where to look. usbmon logs show nothing and I'm attaching dmesg - but I don't think there is any interesting information there. One thing I forgot to say is probably very important is that the audio card only produces the interference when it is being used. So this means that when it is sitting idle (no usbmon output) there is no interference. However, as soon as I start using it (open it with ALSA, or starting a JACK audio server) the cracks and pops start. When I stop the application using it, the cracks and pops stop - and the usbmon output too. I've tried capturing a usbmon log on the DVB adapter part, but no output is produced when the interference starts. Note that I do not need to be using the DVB adapter (streaming from it) in order for the interference to appear. But as soon as I unload the dvb_usb_dib0700 module, it stops the cracks and pops in the audio. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
