Re: USB Mass Storage devices continually reenumerate
Alan Stern <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Tue, 6 Nov 2007, Mike Nuss wrote: > On 11/6/07, Alan Stern <[email protected]> wrote: > > On Mon, 5 Nov 2007, Mike Nuss wrote: > > > Nov 5 14:50:02 usb-storage: Status code -62; transferred 192/65536 > > > Nov 5 14:50:02 usb-storage: -- unknown error > > > Nov 5 14:50:02 End usb_stor_bulk_transfer_sglist: Wait 10s > > > Nov 5 14:50:02 hub 1-0:1.0: state 7 ports 2 chg 0000 evt 0004 > > > Nov 5 14:50:02 ohci_hcd 0000:00:13.0: GetStatus roothub.portstatus > > > [1] = 0x00030101 PESC CSC PPS CCS > > > > Aha! So the controller thinks the device really did signal a > > disconnect condition (CSC is set). > > Good point. Does that mean the kernel should have previously seen a > status report with CSC and no CCS? Or if the disconnect condition was > short enough, would I only see the reconnect status, as above? CCS always reflects the current status. If a disconnect occurs and a reconnect happens very quickly thereafter, the kernel might well miss the intermediate stage where CCS was clear. However I hedged my bets: I said "the controller thinks the device really did signal a disconnect condition". That doesn't necessarily mean there _actually_ was a disconnect -- perhaps the controller was buggy or mistaken. > (It's > not clear to me whether the OHCI root hub status is always polled or > if changes are interrupt-based.) Sometimes polled, sometimes interrupt-based. But interrupt latency can be high enough that you mustn't depend on seeing short-lived intermediate states. Alan Stern ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel