netdev - Re: [PATCH net-next v4 1/2] dts: Add a binding for Synopsys emac max-frame-size

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Date:	Thu, 16 Jan 2014 19:00:45 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Vince Bridgers <vbridgers2013@...il.com>
CC:	<devicetree@...r.kernel.org>, <netdev@...r.kernel.org>,
	Giuseppe CAVALLARO <peppe.cavallaro@...com>,
	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, Kumar Gala <galak@...eaurora.org>,
	Dinh Nguyen <dinguyen@...era.com>,
	"Rayagond Kokatanur" <rayagond@...avyalabs.com>
Subject: Re: [PATCH net-next v4 1/2] dts: Add a binding for Synopsys emac
 max-frame-size

On Thu, 2014-01-16 at 12:48 -0600, Vince Bridgers wrote:
> On Thu, Jan 16, 2014 at 11:50 AM, Ben Hutchings
> <bhutchings@...arflare.com> wrote:
> > On Thu, 2014-01-16 at 08:05 -0600, Vince Bridgers wrote:
> >> This change adds a parameter for the Synopsys 10/100/1000
> >> stmmac Ethernet driver to configure the maximum frame
> >> size supported by the EMAC driver. Synopsys allows the FIFO
> >> sizes to be configured when the cores are built for a particular
> >> device, but do not provide a way for the driver to read
> >> information from the device about the maximum MTU size
> >> supported as limited by the device's FIFO size.
> >>
> >> Signed-off-by: Vince Bridgers <vbridgers2013@...il.com>
> >> ---
> >> V4: add comments to explain use of max-frame-size with respect
> >>     to inconsistent definition and use in the ePAPR v1.1 spec
> >
> > Well, ePAPR does not seem to be consistent with itself. :-)
> >
> >> V3: change snps,max-frame-size to max-frame-size
> >> V2: change snps,max-mtu to snps,max-frame-size
> >> ---
> >>  Documentation/devicetree/bindings/net/stmmac.txt |   13 ++++++++++++-
> >>  1 file changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt
> >> index eba0e5e..d553be2 100644
> >> --- a/Documentation/devicetree/bindings/net/stmmac.txt
> >> +++ b/Documentation/devicetree/bindings/net/stmmac.txt
> >> @@ -29,7 +29,17 @@ Required properties:
> >>                               ignored if force_thresh_dma_mode is set.
> >>
> >>  Optional properties:
> >> -- mac-address: 6 bytes, mac address
> >> +- mac-address:               6 bytes, mac address
> >> +- max-frame-size:    Maximum frame size permitted. This parameter is useful
> >> +                     since different implementations of the Synopsys MAC may
> >> +                     have different FIFO sizes depending on the selections
> >> +                     made in Synopsys Core Consultant. Note that the usage
> >> +                     is inconsistent with the definition in the ePAPR v1.1
> >> +                     specification, as it defines max-frame-size inclusive
> >> +                     of the MAC DA, SA, Ethertype and CRC while usage is
> >> +                     consistent with the IEEE definition of MAC Client
> >> +                     Data, which is sans the MAC DA, SA, Ethertype and
> >> +                     CRC.
> > [...]
> >
> > While this is very precise, I fear that it is now so verbose that it
> > actually becomes confusing.  Can this not be condensed to 'the maximum
> > MTU and MRU, rather than the maximum Ethernet frame size'?
> >
> > Ben.
> 
> Sure, I'll cut this down and resubmit as V5. How about
> 
> "The Maximum Transfer Unit (IEEE defined MTU), rather than the maximum
> frame size."

Sounds good.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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