Alan Stern wrote: >> I've tried a suspend / resume cycle with another USB serial device, a >> Belkin RS-232 serial converter which uses the mct_u232 driver. >> >> And here we're seeing basically the same thing. When initially plugged >> in, it comes up as /dev/ttyUSB0. I can fire up minicom, and talk to >> another RS-232 device. >> >> When the system comes out of suspend, the serial converter is back as >> /dev/ttyUSB1. The minicom application is of course clueless as to what >> has happened, and communication to the other RS-232 device no longer works. >> >> ------------------------------------------------------------------- >> >> So the question in my mind is now this, is it possible to close the >> driver upon suspend? Would this allow the device, when it is "plugged >> back in" to get the same /dev device file(s) it previously had. > > If you exited from minicom or your other application before the > suspend and then restarted it after the resume, you should be okay. Is > that what you're asking?
Yes, if you close the device file, and then do the suspend / resume, then the serial converter will be available again at the same /dev/ttyUSB0. So that's fine. > Just recently added to the mainline GIT tree is a way around your > problem. (It has been in Greg KH's development tree for some time > now.) You can read all about it in Documentation/usb/persist.txt. > > To make this work, your device driver must define a "reset_resume" > method. It will be called in place of the regular "resume" method if > the device has been reset. It can reinitialize the device and put it > back in the original pre-suspend condition, after which it ought to > continue operating normally. The application wouldn't notice a thing, > except perhaps that the serial connection had been lost. OK, that sounds like what we want. I'll clone Greg KH's tree and take a look. I think I should also study the USB storage code, it seems to handle suspend/resume pretty well. You can plug in a USB flash drive, mount it, suspend / resume, and it is still available, and still mounted. Thanks for the pointer, James Graves ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
