Messages in this thread | | | Subject | Re: [PACTH v1] cdc-wdm: Clear read pipeline in case of error | From | Robert Foss <> | Date | Thu, 4 Aug 2016 13:44:29 -0400 |
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On 2016-08-03 06:39 AM, Oliver Neukum wrote: > On Tue, 2016-08-02 at 10:37 -0400, Robert Foss wrote: >> >> On 2016-08-02 09:59 AM, Oliver Neukum wrote: >>> On Tue, 2016-08-02 at 09:54 -0400, Robert Foss wrote: >>>> >>>> On 2016-08-02 08:23 AM, Oliver Neukum wrote: >>>>> On Thu, 2016-07-28 at 14:19 -0400, robert.foss@collabora.com wrote: >>>>>> From: Prathmesh Prabhu <pprabhu@chromium.org> >>>>>> >>>>>> Implemented queued response handling. This queue is processed every >>>>>> time the >>>>>> WDM_READ flag is cleared. >>>>>> >>>>>> In case of a read error, userspace may not actually read the data, >>>>>> since the >>>>>> driver returns an error through wdm_poll. After this, the underlying >>>>>> device may >>>>>> attempt to send us more data, but the queue is not processed. While >>>>>> userspace is >>>>>> also blocked, because the read error is never cleared. >>>>> >>>>> Could you explain why user space cannot just read more data? >>>>> That will clear the error. >>>> >>>> Userspace certainly could read more data, but for the case when >>>> userspace doesn't read and clear a potential an error, we still would >>>> like to not be stuck if the device sends more data. space >>>> >>>> I hope that answers your question, if not I'll try to be more elaborate. >>> >>> Clear, but why does that require the suppression of an error condition? >>> errors should always be delivered. >> >> The goal is not to clear the error condition, but that is required to >> not stay stuck. > > How can that depend on what we return to user space? > In the driver we can continue just ignoring errors. > Now, if user space stops reading because we reported an error, > that is the decision user space has made. We cannot ignore errors > in the kernel because we don't like what user space does when it > sees the error.
So perhaps the better solution is to be more intelligent about how desc->rerr is written to during after an error to be able to maintain the error condition?
> > Regards > Oliver > >
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