On Mon, Jul 6, 2009 at 6:37 PM, Alan Stern<stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 6 Jul 2009, Peter Naulls wrote: > >> On Mon, Jul 6, 2009 at 11:01 AM, Alan Stern<stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Mon, 6 Jul 2009, Peter Naulls wrote: >> > >> >> >> >> >> ttyUSB3 is now missing, which was the device I was trying to use. >> > >> > This is correct behavior, isn't it? Your program is still running and >> > still holding ttyUSB3 open, so that same minor number can't be used for >> > a new device node. >> > >> >> Dubious. It's true that I am still holding it open, but it will eventually be >> let go by pppd et al. Apart from that, it's a departure from behaviour in >> previous kernel versions. > > Not at all; the kernel has always behaved this way. Maybe it's not a > good way, but it hasn't changed. I beg to differ. The software in question has been working for more than a year's worth of kernels. There's something different about 2.6.31-rc2 over 2.6.30 (with your patches). Maybe it's some subtlety I'm now triggering. >> And how do I determine which interface >> is the correct control interface the 3rd, 5th, 10th time it's inserted? > > I don't know. In fact, I don't even know how you can determine the > correct interface the first time. After all, if you had another USB > serial device plugged in earlier then all the ttyUSB numbers would get > bumped up correspondingly. Certainly. See below. > The information may be available in sysfs. It certainly is available > in the system log, but digging it out isn't easy. > >> I don't pretend to be an expert on device allocation etc, in the kernel, >> so please correct me here, but this doesn't seem the best. > > What would you prefer? And what would you do if you had 2 of these > devices? Like you said - and what the code I have already does. Enumerate values in /sys and then look for unique USB IDs. I then know for certain USB IDs that it's the first device (or in the case of various wacky Sierra devices, the nth device). Certainly I assume they're sequential, but that could be changed. But If it's now the 3rd device instead of the 4th after removal and reinsertion, then that's definitely odd. Real world context: this is a 3G router which accepts multiple cards, on which I expect the customer to do all kinds of crazy plugging and unplugging. Maybe I can work around all this, but what I don't have right now is a good characterization of the problem. If you wish, I can get that, but I feel it would be more productive for someone who knows the code be able to describe what should be happening. -- - Peter Naulls -- 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
