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From: Bin Liu <b-liu@ti.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened
Date: Wed, 20 May 2020 13:59:21 -0500
Message-ID: <20200520185921.GE15845@iaqt7> (raw)
In-Reply-To: <20200520182536.GB15590@rowland.harvard.edu>

On Wed, May 20, 2020 at 02:25:36PM -0400, Alan Stern wrote:
> On Wed, May 20, 2020 at 01:05:50PM -0500, Bin Liu wrote:
> > On Wed, May 20, 2020 at 12:40:55PM -0400, Alan Stern wrote:
> > > > > Then do you think we should change the API?
> > > > > 
> > > > > Right now it's a little too complicated.  There's no real reason for 
> > > > > EPROTO, EILSEQ, and ETIME to be different codes.  And now you seem to be 
> > > > > suggesting that we should fold them all into ESHUTDOWN.
> > > > 
> > > > I haven't studied all the USB error code enough to suggest this. I am
> > > > only changing to ESHUTDOWN in musb driver because I know this 3-strikes
> > > > error should only be caused by USB device disabled, which is the
> > > > definition of ESHUTDOWN in error-code.rst.
> > > 
> > > You should spend a little time studying the error-codes document.  
> > > EPROTO, EILSEQ, and ETIME describe different kinds of errors that all 
> > > fall into the 3-strikes category.
> > 
> > But not all device drivers, except the 3 I found, treat EPROTO as fatal,
> > and I cannot fix it in all the device drivers. The only thing I can do
> > at this moment is changing the MUSB HCD driver to return ESHUTDOWN which
> > still follows the document, kind of.
> 
> Think long-term.  Yes, for now you're focused on changing the MUSB HCD.  
> But what should happen in the future?
> 
> At some point we all need to stop reacting and start making some 
> deliberate plans.  This issue is bigger than one patch or one driver.

Yes, the issue big, not all device drivers treat the urb error status
properly. As the case #3 I mentioned earlier, even MUSB HCD returns
ESHUTDOWN, the interrupt storm still happens. Unfortunately before I
located the offending device driver, the remote setup is gone...

I agree with you, we probably should simply the number of the error code
based on the real usecases and the handlings in device drivers.

-Bin.

  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
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 [this message]
2020-05-19 17:28             ` [PATCH v2] " Bin Liu

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