Stupid mail client sent my message mid-writing. Sorry. What happens when you remove a last-non-CP210X device from the hub?
On Tue, Apr 7, 2015 at 10:39 PM, Tal Shorer <tal.sho...@gmail.com> wrote: > Wild guess, you don't see the same behavior on your desktop machine > because it's a different hcd that sets the return value. > What happens when you > > On Tue, Apr 7, 2015 at 9:57 PM, Mark Enstone <mark.enst...@silabs.com> wrote: >> linux-usb, >> >> Apologies if I've come at this the wrong way, I've read MAINTAINERS and >> usb-serial.txt to get your name. >> >> >> Kernel 3.15 added logic to usb_serial_generic_read_bulk_callback() to >> resubmit read URBs in the general/default fail case (for failures other than >> urb->status = ENOENT, ECONNRESET, ESHUTDOWN. Also EPIPE). >> >> On Raspberry Pi, running a 3.18 kernel, I am seeing -EPROTO as the >> urb->status in usb_serial_generic_read_bulk_callback() when the last >> CP210X USB-UART device is removed from a hub (the hub remains attached to >> the Raspberry Pi). ((removing a non-last CP210X from the hub, does not >> return EPROTO, does return one of the specifically identified errnos)). The >> URB is retried, which fails again with EPROTO, is retried, fails in the same >> way again, etc. "forever". >> >> I am not seeing this same behavior on a similarly configured Dell Optiplex >> desktop. Thus far, only on RPi. >> >> >> Question: have you seen such behavior? Had you considered adding EPROTO to >> the list of urb->status errnos failed rather than retried? If I do fail, >> rather than retry, the -EPROTO-failed URB, I get my expected results. I do >> not know what the correct approach is, hoped you could opine: should I add >> EPROTO as a "fail" rather than as a "retry" error in >> usb_serial_generic_read_bulk_callback() (this seems to fix my problem)? Or >> should I investigate why/where the EPROTO is coming from vs. why it is not, >> say, ENOENT (it does not seem unreasonable to retry an EPROTO IFF EPROTO is >> considered transient, however my test case it seems to get "stuck at" >> EPROTO)? >> >> Thoughts appreciated, thank you, >> >> ~Mark >> >> Mark Enstone >> "We are stuck with technology when what we really want is just stuff that >> works" --- DNA >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-usb" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
