netdev - Re: [net-next-2.6 PATCH 6/9] vxge: Check if FCS stripping is disabled by the firmware.

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Message-ID: <4AC9EEE0.5000601@gmail.com>
Date:	Mon, 05 Oct 2009 15:04:32 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sreenivasa Honnur <Sreenivasa.Honnur@...erion.com>
CC:	davem@...emloft.net, netdev@...r.kernel.org, support@...erion.com
Subject: Re: [net-next-2.6 PATCH 6/9] vxge: Check if FCS stripping is disabled
 by the firmware.

Sreenivasa Honnur a écrit :
> - Added a function to check if FCS stripping is disabled by the firmware, if
>   it is not disabled fail driver load.
> 
> - By default FCS stripping is disabled by the firmware. With this assumption
>   driver decrements the indicated packet length by 4 bytes(FCS length).
> 
> - This patch ensures that FCS stripping is disabled during driver load time.
> 
> Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@...erion.com>

What the big deal about FCS not being stripped ?

Denying driver load for this litle detail seems very hard.
You could issue a warning if there is a performance hit, but allow the driver
to function.

If this adapter has the ability to disable/enable it at firmware level,
you might replace

pkt_length -= ETH_FCS_LEN;

by :

pkt_length -= adapter->fcs_length;  

Granted you initialized adapter->fcs_length to 0 or 4 depending on firmware setup.

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