netdev - Re: [PATCH v4] ravb: implement MTU change while device is up

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Message-ID: <e2e24b1b-a175-f0b4-2528-a09d786d380b@cogentembedded.com>
Date:   Thu, 14 Nov 2019 23:38:08 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Ulrich Hecht <uli+renesas@...nd.eu>,
        linux-renesas-soc@...r.kernel.org
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        niklas.soderlund@...natech.se, wsa@...-dreams.de,
        horms@...ge.net.au, magnus.damm@...il.com, geert@...der.be
Subject: Re: [PATCH v4] ravb: implement MTU change while device is up

Hello!

On 11/14/2019 04:49 AM, Ulrich Hecht wrote:

> Pre-allocates buffers sufficient for the maximum supported MTU (2026) in
> order to eliminate the possibility of resource exhaustion when changing the
> MTU while the device is up.
> 
> Signed-off-by: Ulrich Hecht <uli+renesas@...nd.eu>

Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

> ---
>  drivers/net/ethernet/renesas/ravb.h      |  3 ++-
>  drivers/net/ethernet/renesas/ravb_main.c | 26 +++++++++++++-----------
>  2 files changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
> index a9c89d5d8898..9f88b5db4f89 100644
> --- a/drivers/net/ethernet/renesas/ravb.h
> +++ b/drivers/net/ethernet/renesas/ravb.h
> @@ -955,6 +955,8 @@ enum RAVB_QUEUE {
>  #define NUM_RX_QUEUE	2
>  #define NUM_TX_QUEUE	2
>  
> +#define RX_BUF_SZ	(2048 - ETH_FCS_LEN + sizeof(__sum16))

   That's smart but won't scale iff we decide to support e.g. Jumbo frames (the real AVB h/w
supports up to 128 KiB frames.

[...]

MBR, Sergei