netdev - Re: cdc_ncm kernel log spam with trendnet 2.5G USB adapter

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Date:   Tue, 22 Dec 2020 19:01:23 -0800
From:   Roland Dreier <roland@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Oliver Neukum <oliver@...kum.org>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: cdc_ncm kernel log spam with trendnet 2.5G USB adapter

On Tue, Dec 22, 2020 at 6:49 PM Jakub Kicinski <kuba@...nel.org> wrote:

> I'm not sure what the story here is but if this change is expected to
> get into the networking tree we'll need a fresh posting. This sort of
> scissored reply does not get into patchwork.

OK, will resend.  Too bad about patchwork, "git am" drops everything
before scissors lines by default.

> It sounds like you're getting tens of those messages a second, we can
> remove the message but the device is still generating spurious events,
> wasting CPU cycles. Was blocking those events deemed unfeasible?

I certainly don't know enough about the USB CDC class to know why the
spurious messages are showing up or whether they could be suppressed
without a fix in the adapter firmware.  But even ~30 spurious messages
per second doesn't seem so bad for a multi-gig adapter that might be
handling 100,000 or more packets per second.

 - R.