linux-kernel - Re: [PATCH v2] usbnet: do not count empty skbs as errors in rx

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Message-Id: <201009112222.06149.linux@rainbow-software.org>
Date:	Sat, 11 Sep 2010 22:22:03 +0200
From:	Ondrej Zary <linux@...nbow-software.org>
To:	David Brownell <david-b@...bell.net>
Cc:	netdev@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usbnet: do not count empty skbs as errors in rx_process()

On Saturday 11 September 2010 21:07:59 David Brownell wrote:
> --- On Fri, 9/10/10, Ondrej Zary <linux@...nbow-software.org> wrote:
> > From: Ondrej Zary <linux@...nbow-software.org>
> > Subject: [PATCH v2] usbnet: do not count empty skbs as errors in
> > rx_process()
>
> NAK to this backwards-incompatible change.
>
> At this point there's no way to know how many
> drivers it breaks ... I do know that counting
> such SKBs as errors has previously turned up
> link-level errors, and thus led to bugfixes.
>
> > If rx_fixup() returns an empty skb
> > (because it consumed all data inside),
>
> The canonical reason the SKB would be empty is
> because after rx_fixup() removed all header and
> trailer data, there was no packet body left.
> Which is likely a link error, and has been
> worth accounting as such in the past (turned up
> bugs on TX or RX sides).
>
> > do not count it as error.
> >
> > This is needed for cx82310_eth.
>
> I'd far rather see that driver fixed, than see
> the core usbnet framework broken to avoid such
> fixes to a very new driver ...

I already tried to explain that the driver is not broken and so it cannot be 
fixed. It's the way the hardware works and usbnet is not ready for it. I see 
no way to process a packet that crosses URBs (and thus SKBs) without changing 
usbnet.

-- 
Ondrej Zary
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