On Wed, May 11, 2005 at 04:25:03PM -0400, Greg Lee wrote: > Greg, I'm jumping in here with some information that I hope helps a bit.
Don't take people off of the CC: they might not notice :) > I > presently work with several different kernels (2.4.17, 2.4.19, 2.4.21 and a > recent 2.6 kernel which I'm not sure of the version) and have experienced > this problem as well when using usbserial. First, let me define what I see > as "the problem". > > When you interface with mobile phones via USB, they tend to "come and go" > on the USB port due to various events that occur on the phone, the primary > example being power cycling the phone which is something I have to do > regularly for my application. The standard command to switch the power > state on the phone is "AT+CFUN=1" to power it on and "AT+CFUN=0" to power > it off. When you switch the power state the USB port typically disappears > and then reappears several times over the course of 5 seconds or so until > it settles down. Naturally this should invalidate any file descriptors > that you have open for the serial device, however, this does not appear to > work correctly. The symptom that you see is if you write data to the USB > device on a handle that was opened before switching the power state you > will get a kernel OPPS. I work around this by closing the file handle > immediately after sending the AT+CFUN command, waiting 10 seconds and then > attempt to reopen the port. What oops do you get? On a recent 2.6 kernel? And yes, if a device goes away with a open file descriptor, on 2.6, you will get a new usb device node for when the device shows back up. It will not reconnect to the same open file descriptor, sorry. thanks, greg k-h ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_id=7393&alloc_id=16281&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
