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Message-ID: <10dcb1bd-1a61-46e8-81c3-bc87542b72c4@intel.com>
Date: Mon, 11 Mar 2024 15:29:51 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Elad Nachman <enachman@...vell.com>, <taras.chornyi@...ision.eu>,
<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
<pabeni@...hat.com>, <andrew@...n.ch>, <kory.maincent@...tlin.com>,
<thomas.petazzoni@...tlin.com>, <miquel.raynal@...tlin.com>,
<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] net: marvell: prestera: force good base mac
On 3/11/24 14:51, Elad Nachman wrote:
> From: Elad Nachman <enachman@...vell.com>
>
> Since each switchport MAC address uses the switch base mac address
> and adds the physical port number to it,
> Force the last byte of the switch base mac address to be at
> least 128, so when adding to it, we will not wrap around the
to be at *most* 128
> previous (more significant) mac address byte, resulting in a
> warning message.
>
> Signed-off-by: Elad Nachman <enachman@...vell.com>
> ---
> drivers/net/ethernet/marvell/prestera/prestera_main.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/marvell/prestera/prestera_main.c b/drivers/net/ethernet/marvell/prestera/prestera_main.c
> index bcaa8ea27b49..e17b1a24fe18 100644
> --- a/drivers/net/ethernet/marvell/prestera/prestera_main.c
> +++ b/drivers/net/ethernet/marvell/prestera/prestera_main.c
> @@ -859,7 +859,9 @@ static int prestera_switch_set_base_mac_addr(struct prestera_switch *sw)
> if (sw->np)
> ret = of_get_mac_address(sw->np, sw->base_mac);
> if (!is_valid_ether_addr(sw->base_mac) || ret) {
> - eth_random_addr(sw->base_mac);
> + do {
> + eth_random_addr(sw->base_mac);
> + } while (sw->base_mac[5] > 0x80);
Instead of this loop, that uses 6 bytes of random data at each step,
I would just fix the last byte.
Either by calling get_random_u8() in a loop, or perhaps better, just
toggle of MSB unconditionally:
sw->base_mac[5] &= ~0x80; // or '&= 127'
what would change your condition in commit message to "to be at most
127", but I think that should be fine, granted simpler code.
> dev_info(prestera_dev(sw), "using random base mac address\n");
> }
>
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