netdev - Re: [PATCH] ucc_geth: Add 8 bytes to max TX frame for VLANs

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Message-ID: <490DA8B5.2020303@garzik.org>
Date:	Sun, 02 Nov 2008 08:18:45 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Andy Fleming <afleming@...escale.com>
CC:	netdev@...r.kernel.org,
	Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
Subject: Re: [PATCH] ucc_geth: Add 8 bytes to max TX frame for VLANs

Andy Fleming wrote:
> From: Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
> 
> Creating a VLAN interface on top of ucc_geth adds 4 bytes
> to the frame and the HW controller is not prepared to
> TX a frame bigger than 1518 bytes which is 4 bytes too
> small for a full VLAN frame. Also add 4 extra bytes for future
> expansion.
> 
> Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>
> ---
>  drivers/net/ucc_geth.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
> index 8f944e5..8fed4bb 100644
> --- a/drivers/net/ucc_geth.c
> +++ b/drivers/net/ucc_geth.c
> @@ -113,10 +113,10 @@ static struct ucc_geth_info ugeth_primary_info = {
>  	.maxGroupAddrInHash = 4,
>  	.maxIndAddrInHash = 4,
>  	.prel = 7,
> -	.maxFrameLength = 1518,
> +	.maxFrameLength = 1518+8, /* Add 4 bytes for VLAN tags and 4 extra bytes */
>  	.minFrameLength = 64,
> -	.maxD1Length = 1520,
> -	.maxD2Length = 1520,
> +	.maxD1Length = 1520+8,
> +	.maxD2Length = 1520+8,
>  	.vlantype = 0x8100,

Is this still needed?

I found this buried in my inbox.

If so, please resend with the "+8" converted into a named constant. 
Hardcoding lengths like this without named constants (or comments, on 
the other lines) tends to be an error-prone practice.

	Jeff



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