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From: Oliver Neukum <oneukum@suse.com>
To: Alan Stern <stern@rowland.harvard.edu>,
	Martin Kepplinger <martin.kepplinger@puri.sm>
Cc: Oliver Neukum <oneukum@suse.com>, linux-usb@vger.kernel.org
Subject: Re: USB device disconnects on resume
Date: Tue, 3 May 2022 09:36:16 +0200	[thread overview]
Message-ID: <d7a74ca6-589b-61d8-bb5b-aacfb83b6da0@suse.com> (raw)
In-Reply-To: <YnAx3uvVrK4UXd05@rowland.harvard.edu>



On 02.05.22 21:32, Alan Stern wrote:

Hi,

I am happy to help, if I can.
> The usbmon trace shows that quite a lot happens during re-enumeration 
> that doesn't happen during the reset-resume.  No doubt the reason for 
> this is that the cdc-wdm driver doesn't have a real reset-resume 
> handler; the operations it carries out for a reset-resume are the same 
> as for a normal resume, and that clearly is not appropriate here.
Doing reset_resume() for WDM is problematic. The whole point
of WDM as a protocol is to put the configuration of a device
into user space. What is a kernel driver to do in that case.?
> For example, the usbmon trace shows that the kernel sends a 
> Set-Interface request to the modem during re-enumeration and then does a 
> whole lot of probing that I don't understand.  None of this stuff 
> happens during the reset-resume.  Probably the modem decides that 
> without any of this extra configuration, it doesn't need to do 
> anything -- and that's why it disconnects itself.
>

Are you sure that stuff comes from CDC-WDM in the case of reenumeration?
WDM does not do set_interface() in any case.

    Regards
        Oliver


  reply	other threads:[~2022-05-03  7:36 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-19  9:28 USB device disconnects on resume Martin Kepplinger
2022-04-19 14:32 ` Alan Stern
2022-04-20 10:37   ` Martin Kepplinger
2022-04-20 14:40     ` Alan Stern
2022-04-21 10:38       ` Martin Kepplinger
2022-04-21 14:24         ` Alan Stern
2022-04-25  9:45           ` Martin Kepplinger
2022-04-26 14:58             ` Alan Stern
2022-04-28  7:01               ` Martin Kepplinger
2022-04-28 19:13                 ` Alan Stern
2022-04-29 10:15                   ` Martin Kepplinger
2022-04-29 20:21                     ` Alan Stern
     [not found]                       ` <fdc8354e39f9162bcc63ab99f237bdbbe30d6017.camel@puri.sm>
2022-05-02 19:32                         ` Alan Stern
2022-05-03  7:36                           ` Oliver Neukum [this message]
2022-05-03 13:56                             ` Alan Stern

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