From: Bin Liu <email@example.com> To: Alan Stern <firstname.lastname@example.org> Cc: <email@example.com> Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Date: Thu, 14 May 2020 09:28:03 -0500 Message-ID: <20200514142803.GA11463@iaqt7> (raw) In-Reply-To: <20200514013205.GA10515@rowland.harvard.edu> On Wed, May 13, 2020 at 09:32:05PM -0400, Alan Stern wrote: > On Wed, May 13, 2020 at 04:36:20PM -0500, Bin Liu wrote: > > When a USB device attached to a hub got disconnected, MUSB controller > > generates RXCSR_RX_ERROR interrupt for the 3-strikes-out error. > > > > Currently the MUSB host driver returns -EPROTO in current URB, then the > > USB device driver could immediately resubmit the URB which causes MUSB > > generate RXCSR_RX_ERROR interrupt again. This circle causes interrupt > > storm then the hub never got a chance to report the USB device detach. > > > > To fix the interrupt storm, change the URB return code to -ESHUTDOWN for > > MUSB_RXCSR_H_ERROR interrupt, so that the USB device driver will not > > immediately resubmit the URB. > > > > Signed-off-by: Bin Liu <firstname.lastname@example.org> > > Strictly speaking, this is not the right thing to do. It goes against > the API described in error-codes.rst. A better approach would be to fix error-codes.rst says: -ESHUTDOWN The device or host controller has been disabled due to some problem that could not be worked around, such as a physical disconnect. So -ESHUTDOWN is applicable in this case - the device is disconnected behind a hub. > the drivers that immediately resubmit an URB after getting a -EPROTO This has been discussed before . And John indicated there are many device drivers do not delay when resubmitting after getting -EPROTO , and it is quite bit of work to fix it in all device drivers . So better to solve the issue in HCD. > error. After all, that is the wrong thing to do no matter what sort of > host controller the device is attached to.  https://www.spinics.net/lists/linux-usb/msg175292.html  https://www.spinics.net/lists/linux-usb/msg176327.html  https://www.spinics.net/lists/linux-usb/msg176375.html -Bin.
next prev parent reply index Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-13 21:36 Bin Liu 2020-05-14 1:32 ` Alan Stern 2020-05-14 14:28 ` Bin Liu [this message] 2020-05-14 14:40 ` Alan Stern 2020-05-14 15:02 ` Bin Liu 2020-05-14 15:37 ` Bin Liu 2020-05-14 16:26 ` Alan Stern 2020-05-14 17:00 ` Bin Liu 2020-05-14 18:55 ` Alan Stern 2020-05-19 17:12 ` Bin Liu 2020-05-19 20:01 ` Alan Stern 2020-05-20 14:31 ` Bin Liu 2020-05-20 16:40 ` Alan Stern 2020-05-20 18:05 ` Bin Liu 2020-05-20 18:25 ` Alan Stern 2020-05-20 18:59 ` Bin Liu 2020-05-19 17:28 ` [PATCH v2] " Bin Liu
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