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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 09:31:12 -0500
Message-ID: <20200520143112.GB15845@iaqt7> (raw)
In-Reply-To: <20200519200158.GA1339@rowland.harvard.edu>

On Tue, May 19, 2020 at 04:01:58PM -0400, Alan Stern wrote:
> On Tue, May 19, 2020 at 12:12:55PM -0500, Bin Liu wrote:
> > On Thu, May 14, 2020 at 02:55:49PM -0400, Alan Stern wrote:
> > > On Thu, May 14, 2020 at 12:00:23PM -0500, Bin Liu wrote:
> > > 
> > > > > Still, it's worth pointing out that this change abuses the API (perhaps 
> > > > > mentioning it in a comment).  And it still would be preferable to fix 
> > > > 
> > > > Okay, I will add those notes in comment in v2.
> > > > 
> > > > > the drivers in question, impractical though that may be.  (I have a hard 
> > > > > time believing there are really 500 of them getting this wrong...)
> > > > 
> > > > I am not sure about it either, but yeah it is not practical to fix the
> > > > issue in device drivers. So far I have seen 3 reports of this issue:
> > > > 
> > > > 1. with FTDI usb-serial adapter, the issue is in the usb serial generic
> > > > driver;
> > > 
> > > It shouldn't be hard to fix this.  We don't even need a delayed retry; 
> > > the driver can simply treat -EPROTO as an unrecoverable error, just like 
> > > -ESHUTDOWN.
> > 
> > This is just an example showing that it is not practical to fix the
> > problem in device drivers.
> > 
> > BTY, I just briefly searched the drivers/ folder, there are only three
> > drivers handle -EPROTO specifically in rx callback and bail out. So
> > seems most drivers do not care about -EPROTO.
> 
> 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.

-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 [this message]
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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