Hi Greg/Lee,
Thank you very much for the information and yesterday we also had this thought. We are tried it working fine now. This is one of the good solutions. Thanks again. Shalini. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Greg Lee Sent: Thursday, May 12, 2005 1:55 AM To: linux-usb-devel@lists.sourceforge.net Subject: RE: FW: [linux-usb-devel] Usb serial with power ON/OFF problem using Linux 2.6.11.8 > I'm sorry, but I don't see the specs for your device on how > it works. Did you forget to attach them? > > thanks, > > greg k-h Greg, I'm jumping in here with some information that I hope helps a bit. 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. While I do have a workaround, occasionally my software is not able to account for this case and I do end up with kernel OPPS which are caught by the system watchdog. It "would be nice" if I did not have to account for this problem. I have seen a couple of others on this mailing list dealing with similar problems in the past month as well. Regards, Greg Lee [EMAIL PROTECTED] ------------------------------------------------------- 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_ids93&alloc_id281&op=ick _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel ------------------------------------------------------- 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_ids93&alloc_id281&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
